diff --git a/Cargo.lock b/Cargo.lock
index 0241301062db4..aeed169f2d2bb 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2136,7 +2136,6 @@ version = "0.0.0"
 dependencies = [
  "anyhow",
  "colored",
- "once_cell",
  "red_knot_python_semantic",
  "red_knot_vendored",
  "regex",
@@ -2154,7 +2153,6 @@ dependencies = [
 name = "red_knot_vendored"
 version = "0.0.0"
 dependencies = [
- "once_cell",
  "path-slash",
  "ruff_db",
  "walkdir",
@@ -2382,7 +2380,6 @@ dependencies = [
  "codspeed-criterion-compat",
  "criterion",
  "mimalloc",
- "once_cell",
  "rayon",
  "red_knot_python_semantic",
  "red_knot_workspace",
@@ -2515,7 +2512,6 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "clap",
- "once_cell",
  "red_knot_python_semantic",
  "ruff_cache",
  "ruff_db",
@@ -2560,7 +2556,6 @@ dependencies = [
  "log",
  "memchr",
  "natord",
- "once_cell",
  "path-absolutize",
  "pathdiff",
  "pep440_rs 0.6.6",
@@ -2616,7 +2611,6 @@ version = "0.0.0"
 dependencies = [
  "anyhow",
  "itertools 0.13.0",
- "once_cell",
  "rand",
  "ruff_diagnostics",
  "ruff_source_file",
@@ -2638,7 +2632,6 @@ dependencies = [
  "compact_str",
  "is-macro",
  "itertools 0.13.0",
- "once_cell",
  "ruff_cache",
  "ruff_macros",
  "ruff_python_trivia",
@@ -2664,7 +2657,6 @@ dependencies = [
 name = "ruff_python_codegen"
 version = "0.0.0"
 dependencies = [
- "once_cell",
  "ruff_python_ast",
  "ruff_python_literal",
  "ruff_python_parser",
@@ -2682,7 +2674,6 @@ dependencies = [
  "insta",
  "itertools 0.13.0",
  "memchr",
- "once_cell",
  "regex",
  "ruff_cache",
  "ruff_formatter",
@@ -2843,7 +2834,6 @@ name = "ruff_source_file"
 version = "0.0.0"
 dependencies = [
  "memchr",
- "once_cell",
  "ruff_text_size",
  "serde",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index 57c0712e482ff..f741b5c39f6b1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,7 +4,7 @@ resolver = "2"
 
 [workspace.package]
 edition = "2021"
-rust-version = "1.76"
+rust-version = "1.80"
 homepage = "https://docs.astral.sh/ruff"
 documentation = "https://docs.astral.sh/ruff"
 repository = "https://github.com/astral-sh/ruff"
@@ -101,7 +101,6 @@ memchr = { version = "2.7.1" }
 mimalloc = { version = "0.1.39" }
 natord = { version = "1.0.9" }
 notify = { version = "6.1.1" }
-once_cell = { version = "1.19.0" }
 ordermap = { version = "0.5.0" }
 path-absolutize = { version = "3.1.1" }
 path-slash = { version = "0.2.1" }
diff --git a/crates/red_knot_test/Cargo.toml b/crates/red_knot_test/Cargo.toml
index 5fcc0b9143edb..2de1e9a6622f1 100644
--- a/crates/red_knot_test/Cargo.toml
+++ b/crates/red_knot_test/Cargo.toml
@@ -21,7 +21,6 @@ ruff_text_size = { workspace = true }
 
 anyhow = { workspace = true }
 colored = { workspace = true }
-once_cell = { workspace = true }
 regex = { workspace = true }
 rustc-hash = { workspace = true }
 salsa = { workspace = true }
diff --git a/crates/red_knot_test/src/assertion.rs b/crates/red_knot_test/src/assertion.rs
index 160214e36b652..2355b19f2f748 100644
--- a/crates/red_knot_test/src/assertion.rs
+++ b/crates/red_knot_test/src/assertion.rs
@@ -35,7 +35,6 @@
 //! ```
 
 use crate::db::Db;
-use once_cell::sync::Lazy;
 use regex::Regex;
 use ruff_db::files::File;
 use ruff_db::parsed::parsed_module;
@@ -45,6 +44,7 @@ use ruff_source_file::{LineIndex, Locator, OneIndexed};
 use ruff_text_size::{Ranged, TextRange};
 use smallvec::SmallVec;
 use std::ops::Deref;
+use std::sync::LazyLock;
 
 /// Diagnostic assertion comments in a single embedded file.
 #[derive(Debug)]
@@ -239,10 +239,10 @@ impl<'a> Deref for LineAssertions<'a> {
     }
 }
 
-static TYPE_RE: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"^#\s*revealed:\s*(?<ty_display>.+?)\s*$").unwrap());
+static TYPE_RE: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"^#\s*revealed:\s*(?<ty_display>.+?)\s*$").unwrap());
 
-static ERROR_RE: Lazy<Regex> = Lazy::new(|| {
+static ERROR_RE: LazyLock<Regex> = LazyLock::new(|| {
     Regex::new(
         r#"^#\s*error:(\s*(?<column>\d+))?(\s*\[(?<rule>.+?)\])?(\s*"(?<message>.+?)")?\s*$"#,
     )
diff --git a/crates/red_knot_test/src/parser.rs b/crates/red_knot_test/src/parser.rs
index 9d760f9036231..9c5f3a19559da 100644
--- a/crates/red_knot_test/src/parser.rs
+++ b/crates/red_knot_test/src/parser.rs
@@ -1,7 +1,7 @@
-use once_cell::sync::Lazy;
 use regex::{Captures, Regex};
 use ruff_index::{newtype_index, IndexVec};
 use rustc_hash::{FxHashMap, FxHashSet};
+use std::sync::LazyLock;
 
 /// Parse the Markdown `source` as a test suite with given `title`.
 pub(crate) fn parse<'s>(title: &'s str, source: &'s str) -> anyhow::Result<MarkdownTestSuite<'s>> {
@@ -135,12 +135,12 @@ pub(crate) struct EmbeddedFile<'s> {
 
 /// Matches an arbitrary amount of whitespace (including newlines), followed by a sequence of `#`
 /// characters, followed by a title heading, followed by a newline.
-static HEADER_RE: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"^(\s*\n)*(?<level>#+)\s+(?<title>.+)\s*\n").unwrap());
+static HEADER_RE: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"^(\s*\n)*(?<level>#+)\s+(?<title>.+)\s*\n").unwrap());
 
 /// Matches a code block fenced by triple backticks, possibly with language and `key=val`
 /// configuration items following the opening backticks (in the "tag string" of the code block).
-static CODE_RE: Lazy<Regex> = Lazy::new(|| {
+static CODE_RE: LazyLock<Regex> = LazyLock::new(|| {
     Regex::new(r"^```(?<lang>\w+)(?<config>( +\S+)*)\s*\n(?<code>(.|\n)*?)\n?```\s*\n").unwrap()
 });
 
diff --git a/crates/red_knot_vendored/Cargo.toml b/crates/red_knot_vendored/Cargo.toml
index 72c7dd542078e..b740bef3f4db5 100644
--- a/crates/red_knot_vendored/Cargo.toml
+++ b/crates/red_knot_vendored/Cargo.toml
@@ -12,7 +12,6 @@ license = { workspace = true }
 
 [dependencies]
 ruff_db = { workspace = true }
-once_cell = { workspace = true }
 zip = { workspace = true }
 
 [build-dependencies]
diff --git a/crates/red_knot_vendored/src/lib.rs b/crates/red_knot_vendored/src/lib.rs
index de384cd570b97..d1a5816ec2383 100644
--- a/crates/red_knot_vendored/src/lib.rs
+++ b/crates/red_knot_vendored/src/lib.rs
@@ -1,14 +1,13 @@
-use once_cell::sync::Lazy;
-
 use ruff_db::vendored::VendoredFileSystem;
+use std::sync::LazyLock;
 
 // The file path here is hardcoded in this crate's `build.rs` script.
 // Luckily this crate will fail to build if this file isn't available at build time.
 static TYPESHED_ZIP_BYTES: &[u8] = include_bytes!(concat!(env!("OUT_DIR"), "/zipped_typeshed.zip"));
 
 pub fn file_system() -> &'static VendoredFileSystem {
-    static VENDORED_TYPESHED_STUBS: Lazy<VendoredFileSystem> =
-        Lazy::new(|| VendoredFileSystem::new_static(TYPESHED_ZIP_BYTES).unwrap());
+    static VENDORED_TYPESHED_STUBS: LazyLock<VendoredFileSystem> =
+        LazyLock::new(|| VendoredFileSystem::new_static(TYPESHED_ZIP_BYTES).unwrap());
     &VENDORED_TYPESHED_STUBS
 }
 
diff --git a/crates/ruff_benchmark/Cargo.toml b/crates/ruff_benchmark/Cargo.toml
index 05328759cd722..c6c8510145d69 100644
--- a/crates/ruff_benchmark/Cargo.toml
+++ b/crates/ruff_benchmark/Cargo.toml
@@ -39,7 +39,6 @@ harness = false
 [dependencies]
 codspeed-criterion-compat = { workspace = true, default-features = false, optional = true }
 criterion = { workspace = true, default-features = false }
-once_cell = { workspace = true }
 rayon = { workspace = true }
 rustc-hash = { workspace = true }
 serde = { workspace = true }
diff --git a/crates/ruff_benchmark/src/lib.rs b/crates/ruff_benchmark/src/lib.rs
index 5fcf31bf7e586..cb6236c29a1e5 100644
--- a/crates/ruff_benchmark/src/lib.rs
+++ b/crates/ruff_benchmark/src/lib.rs
@@ -82,7 +82,7 @@ impl TestFile {
     }
 }
 
-static TARGET_DIR: once_cell::sync::Lazy<PathBuf> = once_cell::sync::Lazy::new(|| {
+static TARGET_DIR: std::sync::LazyLock<PathBuf> = std::sync::LazyLock::new(|| {
     cargo_target_directory().unwrap_or_else(|| PathBuf::from("target"))
 });
 
diff --git a/crates/ruff_graph/Cargo.toml b/crates/ruff_graph/Cargo.toml
index 9bb0a67d9ca9d..645c9cd2e4255 100644
--- a/crates/ruff_graph/Cargo.toml
+++ b/crates/ruff_graph/Cargo.toml
@@ -20,7 +20,6 @@ ruff_python_parser = { workspace = true }
 
 anyhow = { workspace = true }
 clap = { workspace = true, optional = true }
-once_cell = { workspace = true }
 salsa = { workspace = true }
 schemars = { workspace = true, optional = true }
 serde = { workspace = true, optional = true }
diff --git a/crates/ruff_graph/src/db.rs b/crates/ruff_graph/src/db.rs
index a84168763131f..39f74081bc83d 100644
--- a/crates/ruff_graph/src/db.rs
+++ b/crates/ruff_graph/src/db.rs
@@ -7,12 +7,11 @@ use ruff_db::system::{OsSystem, System, SystemPathBuf};
 use ruff_db::vendored::{VendoredFileSystem, VendoredFileSystemBuilder};
 use ruff_db::{Db as SourceDb, Upcast};
 
-static EMPTY_VENDORED: once_cell::sync::Lazy<VendoredFileSystem> =
-    once_cell::sync::Lazy::new(|| {
-        let mut builder = VendoredFileSystemBuilder::new(CompressionMethod::Stored);
-        builder.add_file("stdlib/VERSIONS", "\n").unwrap();
-        builder.finish().unwrap()
-    });
+static EMPTY_VENDORED: std::sync::LazyLock<VendoredFileSystem> = std::sync::LazyLock::new(|| {
+    let mut builder = VendoredFileSystemBuilder::new(CompressionMethod::Stored);
+    builder.add_file("stdlib/VERSIONS", "\n").unwrap();
+    builder.finish().unwrap()
+});
 
 #[salsa::db]
 #[derive(Default)]
diff --git a/crates/ruff_linter/Cargo.toml b/crates/ruff_linter/Cargo.toml
index eded5f03f457d..6940b1a4268ab 100644
--- a/crates/ruff_linter/Cargo.toml
+++ b/crates/ruff_linter/Cargo.toml
@@ -46,10 +46,9 @@ libcst = { workspace = true }
 log = { workspace = true }
 memchr = { workspace = true }
 natord = { workspace = true }
-once_cell = { workspace = true }
 path-absolutize = { workspace = true, features = [
-  "once_cell_cache",
-  "use_unix_paths_on_wasm",
+    "once_cell_cache",
+    "use_unix_paths_on_wasm",
 ] }
 pathdiff = { workspace = true }
 pep440_rs = { workspace = true, features = ["serde"] }
diff --git a/crates/ruff_linter/src/linter.rs b/crates/ruff_linter/src/linter.rs
index ca7dc608f746c..6958b298cf3a3 100644
--- a/crates/ruff_linter/src/linter.rs
+++ b/crates/ruff_linter/src/linter.rs
@@ -1,4 +1,5 @@
 use std::borrow::Cow;
+use std::cell::LazyCell;
 use std::ops::Deref;
 use std::path::Path;
 
@@ -440,7 +441,7 @@ fn diagnostics_to_messages(
     locator: &Locator,
     directives: &Directives,
 ) -> Vec<Message> {
-    let file = once_cell::unsync::Lazy::new(|| {
+    let file = LazyCell::new(|| {
         let mut builder =
             SourceFileBuilder::new(path.to_string_lossy().as_ref(), locator.contents());
 
diff --git a/crates/ruff_linter/src/logging.rs b/crates/ruff_linter/src/logging.rs
index ce89402231ffc..4d88c637bcc43 100644
--- a/crates/ruff_linter/src/logging.rs
+++ b/crates/ruff_linter/src/logging.rs
@@ -1,12 +1,11 @@
 use std::fmt::{Display, Formatter, Write};
 use std::path::{Path, PathBuf};
-use std::sync::Mutex;
+use std::sync::{LazyLock, Mutex};
 
 use anyhow::Result;
 use colored::Colorize;
 use fern;
 use log::Level;
-use once_cell::sync::Lazy;
 use ruff_python_parser::{ParseError, ParseErrorType};
 use rustc_hash::FxHashSet;
 
@@ -16,7 +15,7 @@ use crate::fs;
 use crate::source_kind::SourceKind;
 use ruff_notebook::Notebook;
 
-pub static IDENTIFIERS: Lazy<Mutex<Vec<&'static str>>> = Lazy::new(Mutex::default);
+pub static IDENTIFIERS: LazyLock<Mutex<Vec<&'static str>>> = LazyLock::new(Mutex::default);
 
 /// Warn a user once, with uniqueness determined by the given ID.
 #[macro_export]
@@ -35,7 +34,7 @@ macro_rules! warn_user_once_by_id {
     };
 }
 
-pub static MESSAGES: Lazy<Mutex<FxHashSet<String>>> = Lazy::new(Mutex::default);
+pub static MESSAGES: LazyLock<Mutex<FxHashSet<String>>> = LazyLock::new(Mutex::default);
 
 /// Warn a user once, if warnings are enabled, with uniqueness determined by the content of the
 /// message.
diff --git a/crates/ruff_linter/src/rule_redirects.rs b/crates/ruff_linter/src/rule_redirects.rs
index ab5ae7c7a7008..ccbd4ca571627 100644
--- a/crates/ruff_linter/src/rule_redirects.rs
+++ b/crates/ruff_linter/src/rule_redirects.rs
@@ -1,6 +1,5 @@
 use std::collections::HashMap;
-
-use once_cell::sync::Lazy;
+use std::sync::LazyLock;
 
 /// Returns the redirect target for the given code.
 pub(crate) fn get_redirect_target(code: &str) -> Option<&'static str> {
@@ -13,7 +12,7 @@ pub(crate) fn get_redirect(code: &str) -> Option<(&'static str, &'static str)> {
     REDIRECTS.get_key_value(code).map(|(k, v)| (*k, *v))
 }
 
-static REDIRECTS: Lazy<HashMap<&'static str, &'static str>> = Lazy::new(|| {
+static REDIRECTS: LazyLock<HashMap<&'static str, &'static str>> = LazyLock::new(|| {
     HashMap::from_iter([
         // The following are here because we don't yet have the many-to-one mapping enabled.
         ("SIM111", "SIM110"),
diff --git a/crates/ruff_linter/src/rules/eradicate/detection.rs b/crates/ruff_linter/src/rules/eradicate/detection.rs
index f10efcaf5b212..c3ba54a199350 100644
--- a/crates/ruff_linter/src/rules/eradicate/detection.rs
+++ b/crates/ruff_linter/src/rules/eradicate/detection.rs
@@ -1,29 +1,28 @@
 /// See: [eradicate.py](https://github.com/myint/eradicate/blob/98f199940979c94447a461d50d27862b118b282d/eradicate.py)
 use aho_corasick::AhoCorasick;
 use itertools::Itertools;
-use once_cell::sync::Lazy;
 use regex::{Regex, RegexSet};
-
 use ruff_python_parser::parse_module;
 use ruff_python_trivia::{SimpleTokenKind, SimpleTokenizer};
 use ruff_text_size::TextSize;
+use std::sync::LazyLock;
 
-static CODE_INDICATORS: Lazy<AhoCorasick> = Lazy::new(|| {
+static CODE_INDICATORS: LazyLock<AhoCorasick> = LazyLock::new(|| {
     AhoCorasick::new([
         "(", ")", "[", "]", "{", "}", ":", "=", "%", "return", "break", "continue", "import",
     ])
     .unwrap()
 });
 
-static ALLOWLIST_REGEX: Lazy<Regex> = Lazy::new(|| {
+static ALLOWLIST_REGEX: LazyLock<Regex> = LazyLock::new(|| {
     Regex::new(
         r"^(?i)(?:pylint|pyright|noqa|nosec|region|endregion|type:\s*ignore|fmt:\s*(on|off)|isort:\s*(on|off|skip|skip_file|split|dont-add-imports(:\s*\[.*?])?)|mypy:|SPDX-License-Identifier:|(?:en)?coding[:=][ \t]*([-_.a-zA-Z0-9]+))",
     ).unwrap()
 });
 
-static HASH_NUMBER: Lazy<Regex> = Lazy::new(|| Regex::new(r"#\d").unwrap());
+static HASH_NUMBER: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"#\d").unwrap());
 
-static POSITIVE_CASES: Lazy<RegexSet> = Lazy::new(|| {
+static POSITIVE_CASES: LazyLock<RegexSet> = LazyLock::new(|| {
     RegexSet::new([
         // Keywords
         r"^(?:elif\s+.*\s*:.*|else\s*:.*|try\s*:.*|finally\s*:.*|except.*:.*|case\s+.*\s*:.*)$",
diff --git a/crates/ruff_linter/src/rules/flake8_bandit/helpers.rs b/crates/ruff_linter/src/rules/flake8_bandit/helpers.rs
index 9f287804ff68d..a79d707f8aa13 100644
--- a/crates/ruff_linter/src/rules/flake8_bandit/helpers.rs
+++ b/crates/ruff_linter/src/rules/flake8_bandit/helpers.rs
@@ -1,10 +1,10 @@
-use once_cell::sync::Lazy;
 use regex::Regex;
 use ruff_python_ast::{self as ast, Expr};
+use std::sync::LazyLock;
 
 use ruff_python_semantic::SemanticModel;
 
-static PASSWORD_CANDIDATE_REGEX: Lazy<Regex> = Lazy::new(|| {
+static PASSWORD_CANDIDATE_REGEX: LazyLock<Regex> = LazyLock::new(|| {
     Regex::new(r"(^|_)(?i)(pas+wo?r?d|pass(phrase)?|pwd|token|secrete?)($|_)").unwrap()
 });
 
diff --git a/crates/ruff_linter/src/rules/flake8_bandit/rules/hardcoded_sql_expression.rs b/crates/ruff_linter/src/rules/flake8_bandit/rules/hardcoded_sql_expression.rs
index 670c7d406fcf1..e68d0dcce5f07 100644
--- a/crates/ruff_linter/src/rules/flake8_bandit/rules/hardcoded_sql_expression.rs
+++ b/crates/ruff_linter/src/rules/flake8_bandit/rules/hardcoded_sql_expression.rs
@@ -1,5 +1,7 @@
-use once_cell::sync::Lazy;
+use std::sync::LazyLock;
+
 use regex::Regex;
+
 use ruff_diagnostics::{Diagnostic, Violation};
 use ruff_macros::{derive_message_formats, violation};
 use ruff_python_ast::str::raw_contents;
@@ -9,7 +11,7 @@ use ruff_text_size::Ranged;
 
 use crate::checkers::ast::Checker;
 
-static SQL_REGEX: Lazy<Regex> = Lazy::new(|| {
+static SQL_REGEX: LazyLock<Regex> = LazyLock::new(|| {
     Regex::new(r"(?i)\b(select\s+.*\s+from\s|delete\s+from\s|(insert|replace)\s+.*\s+values\s|update\s+.*\s+set\s)")
     .unwrap()
 });
diff --git a/crates/ruff_linter/src/rules/flake8_copyright/settings.rs b/crates/ruff_linter/src/rules/flake8_copyright/settings.rs
index 03551b0a0a93f..8eb50bc0a39b0 100644
--- a/crates/ruff_linter/src/rules/flake8_copyright/settings.rs
+++ b/crates/ruff_linter/src/rules/flake8_copyright/settings.rs
@@ -1,12 +1,14 @@
 //! Settings for the `flake8-copyright` plugin.
 
-use once_cell::sync::Lazy;
-use regex::Regex;
 use std::fmt::{Display, Formatter};
+use std::sync::LazyLock;
+
+use regex::Regex;
 
-use crate::display_settings;
 use ruff_macros::CacheKey;
 
+use crate::display_settings;
+
 #[derive(Debug, Clone, CacheKey)]
 pub struct Settings {
     pub notice_rgx: Regex,
@@ -14,8 +16,8 @@ pub struct Settings {
     pub min_file_size: usize,
 }
 
-pub static COPYRIGHT: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"(?i)Copyright\s+((?:\(C\)|©)\s+)?\d{4}((-|,\s)\d{4})*").unwrap());
+pub static COPYRIGHT: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"(?i)Copyright\s+((?:\(C\)|©)\s+)?\d{4}((-|,\s)\d{4})*").unwrap());
 
 impl Default for Settings {
     fn default() -> Self {
diff --git a/crates/ruff_linter/src/rules/flake8_pyi/rules/type_comment_in_stub.rs b/crates/ruff_linter/src/rules/flake8_pyi/rules/type_comment_in_stub.rs
index ddb8acd333631..719e4b6212f0b 100644
--- a/crates/ruff_linter/src/rules/flake8_pyi/rules/type_comment_in_stub.rs
+++ b/crates/ruff_linter/src/rules/flake8_pyi/rules/type_comment_in_stub.rs
@@ -1,7 +1,7 @@
-use once_cell::sync::Lazy;
 use regex::Regex;
 use ruff_python_trivia::CommentRanges;
 use ruff_source_file::Locator;
+use std::sync::LazyLock;
 
 use ruff_diagnostics::{Diagnostic, Violation};
 use ruff_macros::{derive_message_formats, violation};
@@ -49,8 +49,8 @@ pub(crate) fn type_comment_in_stub(
     }
 }
 
-static TYPE_COMMENT_REGEX: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"^#\s*type:\s*([^#]+)(\s*#.*?)?$").unwrap());
+static TYPE_COMMENT_REGEX: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"^#\s*type:\s*([^#]+)(\s*#.*?)?$").unwrap());
 
-static TYPE_IGNORE_REGEX: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"^#\s*type:\s*ignore([^#]+)?(\s*#.*?)?$").unwrap());
+static TYPE_IGNORE_REGEX: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"^#\s*type:\s*ignore([^#]+)?(\s*#.*?)?$").unwrap());
diff --git a/crates/ruff_linter/src/rules/flake8_todos/rules/todos.rs b/crates/ruff_linter/src/rules/flake8_todos/rules/todos.rs
index 35f1d6039fcf9..491d94a2f217c 100644
--- a/crates/ruff_linter/src/rules/flake8_todos/rules/todos.rs
+++ b/crates/ruff_linter/src/rules/flake8_todos/rules/todos.rs
@@ -1,8 +1,8 @@
-use once_cell::sync::Lazy;
 use regex::RegexSet;
 use ruff_python_trivia::CommentRanges;
 use ruff_source_file::Locator;
 use ruff_text_size::{TextLen, TextRange, TextSize};
+use std::sync::LazyLock;
 
 use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix, Violation};
 use ruff_macros::{derive_message_formats, violation};
@@ -222,7 +222,7 @@ impl Violation for MissingSpaceAfterTodoColon {
     }
 }
 
-static ISSUE_LINK_REGEX_SET: Lazy<RegexSet> = Lazy::new(|| {
+static ISSUE_LINK_REGEX_SET: LazyLock<RegexSet> = LazyLock::new(|| {
     RegexSet::new([
         r"^#\s*(http|https)://.*", // issue link
         r"^#\s*\d+$",              // issue code - like "003"
diff --git a/crates/ruff_linter/src/rules/pydocstyle/rules/blank_before_after_function.rs b/crates/ruff_linter/src/rules/pydocstyle/rules/blank_before_after_function.rs
index 25e335e80eb62..11027c562dee3 100644
--- a/crates/ruff_linter/src/rules/pydocstyle/rules/blank_before_after_function.rs
+++ b/crates/ruff_linter/src/rules/pydocstyle/rules/blank_before_after_function.rs
@@ -1,5 +1,5 @@
-use once_cell::sync::Lazy;
 use regex::Regex;
+use std::sync::LazyLock;
 
 use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix};
 use ruff_macros::{derive_message_formats, violation};
@@ -98,8 +98,8 @@ impl AlwaysFixableViolation for NoBlankLineAfterFunction {
     }
 }
 
-static INNER_FUNCTION_OR_CLASS_REGEX: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"^\s+(?:(?:class|def|async def)\s|@)").unwrap());
+static INNER_FUNCTION_OR_CLASS_REGEX: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"^\s+(?:(?:class|def|async def)\s|@)").unwrap());
 
 /// D201, D202
 pub(crate) fn blank_before_after_function(checker: &mut Checker, docstring: &Docstring) {
diff --git a/crates/ruff_linter/src/rules/pydocstyle/rules/non_imperative_mood.rs b/crates/ruff_linter/src/rules/pydocstyle/rules/non_imperative_mood.rs
index 2391aeb11a131..7be580cd1b496 100644
--- a/crates/ruff_linter/src/rules/pydocstyle/rules/non_imperative_mood.rs
+++ b/crates/ruff_linter/src/rules/pydocstyle/rules/non_imperative_mood.rs
@@ -1,5 +1,6 @@
+use std::sync::LazyLock;
+
 use imperative::Mood;
-use once_cell::sync::Lazy;
 
 use ruff_diagnostics::{Diagnostic, Violation};
 use ruff_macros::{derive_message_formats, violation};
@@ -12,7 +13,7 @@ use crate::docstrings::Docstring;
 use crate::rules::pydocstyle::helpers::normalize_word;
 use crate::rules::pydocstyle::settings::Settings;
 
-static MOOD: Lazy<Mood> = Lazy::new(Mood::new);
+static MOOD: LazyLock<Mood> = LazyLock::new(Mood::new);
 
 /// ## What it does
 /// Checks for docstring first lines that are not in an imperative mood.
diff --git a/crates/ruff_linter/src/rules/pydocstyle/rules/sections.rs b/crates/ruff_linter/src/rules/pydocstyle/rules/sections.rs
index 10346ec19482a..e18d7948ea1bd 100644
--- a/crates/ruff_linter/src/rules/pydocstyle/rules/sections.rs
+++ b/crates/ruff_linter/src/rules/pydocstyle/rules/sections.rs
@@ -1,7 +1,7 @@
 use itertools::Itertools;
-use once_cell::sync::Lazy;
 use regex::Regex;
 use rustc_hash::FxHashSet;
+use std::sync::LazyLock;
 
 use ruff_diagnostics::{AlwaysFixableViolation, Violation};
 use ruff_diagnostics::{Diagnostic, Edit, Fix};
@@ -1846,8 +1846,8 @@ fn missing_args(checker: &mut Checker, docstring: &Docstring, docstrings_args: &
 }
 
 // See: `GOOGLE_ARGS_REGEX` in `pydocstyle/checker.py`.
-static GOOGLE_ARGS_REGEX: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"^\s*(\*?\*?\w+)\s*(\(.*?\))?\s*:(\r\n|\n)?\s*.+").unwrap());
+static GOOGLE_ARGS_REGEX: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"^\s*(\*?\*?\w+)\s*(\(.*?\))?\s*:(\r\n|\n)?\s*.+").unwrap());
 
 fn args_section(context: &SectionContext) -> FxHashSet<String> {
     let mut following_lines = context.following_lines().peekable();
diff --git a/crates/ruff_linter/src/rules/pygrep_hooks/rules/blanket_type_ignore.rs b/crates/ruff_linter/src/rules/pygrep_hooks/rules/blanket_type_ignore.rs
index 1fd73eb5c661e..662d76709968f 100644
--- a/crates/ruff_linter/src/rules/pygrep_hooks/rules/blanket_type_ignore.rs
+++ b/crates/ruff_linter/src/rules/pygrep_hooks/rules/blanket_type_ignore.rs
@@ -1,7 +1,7 @@
 use anyhow::{anyhow, Result};
 use memchr::memchr_iter;
-use once_cell::sync::Lazy;
 use regex::Regex;
+use std::sync::LazyLock;
 
 use ruff_diagnostics::{Diagnostic, Violation};
 use ruff_macros::{derive_message_formats, violation};
@@ -102,8 +102,8 @@ pub(crate) fn blanket_type_ignore(
 
 // Match, e.g., `[attr-defined]` or `[attr-defined, misc]`.
 // See: https://github.com/python/mypy/blob/b43e0d34247a6d1b3b9d9094d184bbfcb9808bb9/mypy/fastparse.py#L327
-static TYPE_IGNORE_TAG_PATTERN: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"^\s*\[(?P<codes>[^]#]*)]\s*(#.*)?$").unwrap());
+static TYPE_IGNORE_TAG_PATTERN: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"^\s*\[(?P<codes>[^]#]*)]\s*(#.*)?$").unwrap());
 
 /// Parse the optional `[...]` tag in a `# type: ignore[...]` comment.
 ///
diff --git a/crates/ruff_linter/src/rules/pyupgrade/helpers.rs b/crates/ruff_linter/src/rules/pyupgrade/helpers.rs
index 07196a9127332..84108102078f4 100644
--- a/crates/ruff_linter/src/rules/pyupgrade/helpers.rs
+++ b/crates/ruff_linter/src/rules/pyupgrade/helpers.rs
@@ -1,8 +1,9 @@
-use once_cell::sync::Lazy;
 use regex::{Captures, Regex};
 use std::borrow::Cow;
+use std::sync::LazyLock;
 
-static CURLY_BRACES: Lazy<Regex> = Lazy::new(|| Regex::new(r"(\\N\{[^}]+})|([{}])").unwrap());
+static CURLY_BRACES: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"(\\N\{[^}]+})|([{}])").unwrap());
 
 pub(super) fn curly_escape(text: &str) -> Cow<'_, str> {
     // Match all curly braces. This will include named unicode escapes (like
@@ -20,7 +21,8 @@ pub(super) fn curly_escape(text: &str) -> Cow<'_, str> {
     })
 }
 
-static DOUBLE_CURLY_BRACES: Lazy<Regex> = Lazy::new(|| Regex::new(r"((\{\{)|(\}\}))").unwrap());
+static DOUBLE_CURLY_BRACES: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"((\{\{)|(\}\}))").unwrap());
 
 pub(super) fn curly_unescape(text: &str) -> Cow<'_, str> {
     // Match all double curly braces and replace with a single
diff --git a/crates/ruff_linter/src/rules/pyupgrade/rules/deprecated_unittest_alias.rs b/crates/ruff_linter/src/rules/pyupgrade/rules/deprecated_unittest_alias.rs
index 6205df6ec0fc8..431ef71b90fac 100644
--- a/crates/ruff_linter/src/rules/pyupgrade/rules/deprecated_unittest_alias.rs
+++ b/crates/ruff_linter/src/rules/pyupgrade/rules/deprecated_unittest_alias.rs
@@ -1,6 +1,6 @@
-use once_cell::sync::Lazy;
 use ruff_python_ast::{self as ast, Expr};
 use rustc_hash::FxHashMap;
+use std::sync::LazyLock;
 
 use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix};
 use ruff_macros::{derive_message_formats, violation};
@@ -57,7 +57,7 @@ impl AlwaysFixableViolation for DeprecatedUnittestAlias {
     }
 }
 
-static DEPRECATED_ALIASES: Lazy<FxHashMap<&'static str, &'static str>> = Lazy::new(|| {
+static DEPRECATED_ALIASES: LazyLock<FxHashMap<&'static str, &'static str>> = LazyLock::new(|| {
     FxHashMap::from_iter([
         ("assertAlmostEquals", "assertAlmostEqual"),
         ("assertEquals", "assertEqual"),
diff --git a/crates/ruff_linter/src/rules/pyupgrade/rules/format_literals.rs b/crates/ruff_linter/src/rules/pyupgrade/rules/format_literals.rs
index ab6753f0c8ad3..dd1f4e943d6f4 100644
--- a/crates/ruff_linter/src/rules/pyupgrade/rules/format_literals.rs
+++ b/crates/ruff_linter/src/rules/pyupgrade/rules/format_literals.rs
@@ -1,7 +1,7 @@
 use anyhow::{anyhow, Result};
 use libcst_native::{Arg, Expression};
-use once_cell::sync::Lazy;
 use regex::Regex;
+use std::sync::LazyLock;
 
 use ruff_diagnostics::{Diagnostic, Edit, Fix, FixAvailability, Violation};
 use ruff_macros::{derive_message_formats, violation};
@@ -127,8 +127,8 @@ fn is_sequential(indices: &[usize]) -> bool {
 
 // An opening curly brace, followed by any integer, followed by any text,
 // followed by a closing brace.
-static FORMAT_SPECIFIER: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"\{(?P<int>\d+)(?P<fmt>.*?)}").unwrap());
+static FORMAT_SPECIFIER: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"\{(?P<int>\d+)(?P<fmt>.*?)}").unwrap());
 
 /// Remove the explicit positional indices from a format string.
 fn remove_specifiers<'a>(value: &mut Expression<'a>, arena: &'a typed_arena::Arena<String>) {
diff --git a/crates/ruff_linter/src/rules/pyupgrade/rules/unnecessary_coding_comment.rs b/crates/ruff_linter/src/rules/pyupgrade/rules/unnecessary_coding_comment.rs
index 68b0ee777f391..f48c05a474264 100644
--- a/crates/ruff_linter/src/rules/pyupgrade/rules/unnecessary_coding_comment.rs
+++ b/crates/ruff_linter/src/rules/pyupgrade/rules/unnecessary_coding_comment.rs
@@ -1,5 +1,5 @@
-use once_cell::sync::Lazy;
 use regex::Regex;
+use std::sync::LazyLock;
 
 use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix};
 use ruff_macros::{derive_message_formats, violation};
@@ -42,8 +42,8 @@ impl AlwaysFixableViolation for UTF8EncodingDeclaration {
 }
 
 // Regex from PEP263.
-static CODING_COMMENT_REGEX: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"^[ \t\f]*#.*?coding[:=][ \t]*utf-?8").unwrap());
+static CODING_COMMENT_REGEX: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"^[ \t\f]*#.*?coding[:=][ \t]*utf-?8").unwrap());
 
 /// UP009
 pub(crate) fn unnecessary_coding_comment(
diff --git a/crates/ruff_linter/src/settings/mod.rs b/crates/ruff_linter/src/settings/mod.rs
index 06e6239bf0c0f..2bc98bc930a8f 100644
--- a/crates/ruff_linter/src/settings/mod.rs
+++ b/crates/ruff_linter/src/settings/mod.rs
@@ -2,13 +2,12 @@
 //! command-line options. Structure is optimized for internal usage, as opposed
 //! to external visibility or parsing.
 
-use std::fmt::{Display, Formatter};
-use std::path::{Path, PathBuf};
-
-use once_cell::sync::Lazy;
 use path_absolutize::path_dedot;
 use regex::Regex;
 use rustc_hash::FxHashSet;
+use std::fmt::{Display, Formatter};
+use std::path::{Path, PathBuf};
+use std::sync::LazyLock;
 
 use crate::codes::RuleCodePrefix;
 use ruff_macros::CacheKey;
@@ -355,8 +354,8 @@ pub const DEFAULT_SELECTORS: &[RuleSelector] = &[
 
 pub const TASK_TAGS: &[&str] = &["TODO", "FIXME", "XXX"];
 
-pub static DUMMY_VARIABLE_RGX: Lazy<Regex> =
-    Lazy::new(|| Regex::new("^(_+|(_+[a-zA-Z0-9_]*[a-zA-Z0-9]+?))$").unwrap());
+pub static DUMMY_VARIABLE_RGX: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new("^(_+|(_+[a-zA-Z0-9_]*[a-zA-Z0-9]+?))$").unwrap());
 
 impl LinterSettings {
     pub fn for_rule(rule_code: Rule) -> Self {
diff --git a/crates/ruff_notebook/Cargo.toml b/crates/ruff_notebook/Cargo.toml
index 6de68f30415dd..c8273399edfaa 100644
--- a/crates/ruff_notebook/Cargo.toml
+++ b/crates/ruff_notebook/Cargo.toml
@@ -20,7 +20,6 @@ ruff_text_size = { workspace = true }
 
 anyhow = { workspace = true }
 itertools = { workspace = true }
-once_cell = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
 serde_with = { workspace = true, default-features = false, features = ["macros"] }
diff --git a/crates/ruff_notebook/src/notebook.rs b/crates/ruff_notebook/src/notebook.rs
index 9098227f7c2d4..3ec9108e0373d 100644
--- a/crates/ruff_notebook/src/notebook.rs
+++ b/crates/ruff_notebook/src/notebook.rs
@@ -1,15 +1,14 @@
+use itertools::Itertools;
+use rand::{Rng, SeedableRng};
+use serde::Serialize;
+use serde_json::error::Category;
 use std::cmp::Ordering;
 use std::collections::HashSet;
 use std::fs::File;
 use std::io::{BufReader, Cursor, Read, Seek, SeekFrom, Write};
 use std::path::Path;
+use std::sync::OnceLock;
 use std::{io, iter};
-
-use itertools::Itertools;
-use once_cell::sync::OnceCell;
-use rand::{Rng, SeedableRng};
-use serde::Serialize;
-use serde_json::error::Category;
 use thiserror::Error;
 
 use ruff_diagnostics::{SourceMap, SourceMarker};
@@ -63,7 +62,7 @@ pub struct Notebook {
     source_code: String,
     /// The index of the notebook. This is used to map between the concatenated
     /// source code and the original notebook.
-    index: OnceCell<NotebookIndex>,
+    index: OnceLock<NotebookIndex>,
     /// The raw notebook i.e., the deserialized version of JSON string.
     raw: RawNotebook,
     /// The offsets of each cell in the concatenated source code. This includes
@@ -194,7 +193,7 @@ impl Notebook {
 
         Ok(Self {
             raw: raw_notebook,
-            index: OnceCell::new(),
+            index: OnceLock::new(),
             // The additional newline at the end is to maintain consistency for
             // all cells. These newlines will be removed before updating the
             // source code with the transformed content. Refer `update_cell_content`.
diff --git a/crates/ruff_python_ast/Cargo.toml b/crates/ruff_python_ast/Cargo.toml
index 401f56975cba9..497782a4eef59 100644
--- a/crates/ruff_python_ast/Cargo.toml
+++ b/crates/ruff_python_ast/Cargo.toml
@@ -23,7 +23,6 @@ aho-corasick = { workspace = true }
 bitflags = { workspace = true }
 is-macro = { workspace = true }
 itertools = { workspace = true }
-once_cell = { workspace = true }
 rustc-hash = { workspace = true }
 schemars = { workspace = true, optional = true }
 serde = { workspace = true, optional = true }
diff --git a/crates/ruff_python_ast/src/str.rs b/crates/ruff_python_ast/src/str.rs
index 220df07857f70..13a08d2ccc793 100644
--- a/crates/ruff_python_ast/src/str.rs
+++ b/crates/ruff_python_ast/src/str.rs
@@ -1,7 +1,6 @@
-use std::fmt;
-
 use aho_corasick::{AhoCorasick, AhoCorasickKind, Anchored, Input, MatchKind, StartKind};
-use once_cell::sync::Lazy;
+use std::fmt;
+use std::sync::LazyLock;
 
 use ruff_text_size::{TextLen, TextRange};
 
@@ -205,7 +204,7 @@ pub fn raw_contents_range(contents: &str) -> Option<TextRange> {
 }
 
 /// An [`AhoCorasick`] matcher for string and byte literal prefixes.
-static PREFIX_MATCHER: Lazy<AhoCorasick> = Lazy::new(|| {
+static PREFIX_MATCHER: LazyLock<AhoCorasick> = LazyLock::new(|| {
     AhoCorasick::builder()
         .start_kind(StartKind::Anchored)
         .match_kind(MatchKind::LeftmostLongest)
diff --git a/crates/ruff_python_codegen/Cargo.toml b/crates/ruff_python_codegen/Cargo.toml
index cf273027bb79d..35dcbc30116d9 100644
--- a/crates/ruff_python_codegen/Cargo.toml
+++ b/crates/ruff_python_codegen/Cargo.toml
@@ -20,7 +20,6 @@ ruff_python_parser = { workspace = true }
 ruff_source_file = { workspace = true }
 ruff_text_size = { workspace = true }
 
-once_cell = { workspace = true }
 
 [lints]
 workspace = true
diff --git a/crates/ruff_python_codegen/src/stylist.rs b/crates/ruff_python_codegen/src/stylist.rs
index ea37492c2f0dd..b78417add2971 100644
--- a/crates/ruff_python_codegen/src/stylist.rs
+++ b/crates/ruff_python_codegen/src/stylist.rs
@@ -1,9 +1,8 @@
 //! Detect code style from Python source code.
 
+use std::cell::OnceCell;
 use std::ops::Deref;
 
-use once_cell::unsync::OnceCell;
-
 use ruff_python_ast::str::Quote;
 use ruff_python_parser::{Token, TokenKind, Tokens};
 use ruff_source_file::{find_newline, LineEnding, Locator};
diff --git a/crates/ruff_python_formatter/Cargo.toml b/crates/ruff_python_formatter/Cargo.toml
index befb78e31f4ff..3341f94027c70 100644
--- a/crates/ruff_python_formatter/Cargo.toml
+++ b/crates/ruff_python_formatter/Cargo.toml
@@ -28,7 +28,6 @@ clap = { workspace = true }
 countme = { workspace = true }
 itertools = { workspace = true }
 memchr = { workspace = true }
-once_cell = { workspace = true }
 regex = { workspace = true }
 rustc-hash = { workspace = true }
 serde = { workspace = true, optional = true }
diff --git a/crates/ruff_python_formatter/src/string/docstring.rs b/crates/ruff_python_formatter/src/string/docstring.rs
index 5c177a0142acd..bb1afeee76454 100644
--- a/crates/ruff_python_formatter/src/string/docstring.rs
+++ b/crates/ruff_python_formatter/src/string/docstring.rs
@@ -2,15 +2,15 @@
 // "reStructuredText."
 #![allow(clippy::doc_markdown)]
 
+use itertools::Itertools;
 use std::cmp::Ordering;
+use std::sync::LazyLock;
 use std::{borrow::Cow, collections::VecDeque};
 
-use itertools::Itertools;
-
+use regex::Regex;
 use ruff_formatter::printer::SourceMapGeneration;
 use ruff_python_ast::{str::Quote, StringFlags};
 use ruff_python_trivia::CommentRanges;
-use {once_cell::sync::Lazy, regex::Regex};
 use {
     ruff_formatter::{write, FormatOptions, IndentStyle, LineWidth, Printed},
     ruff_python_trivia::{is_python_whitespace, PythonWhitespace},
@@ -1075,7 +1075,7 @@ impl<'src> CodeExampleRst<'src> {
         // [directives]: https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#directives
         // [Pygments lexer names]: https://pygments.org/docs/lexers/
         // [code-block]: https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#directive-code-block
-        static DIRECTIVE_START: Lazy<Regex> = Lazy::new(|| {
+        static DIRECTIVE_START: LazyLock<Regex> = LazyLock::new(|| {
             Regex::new(
                 r"(?m)^\s*\.\. \s*(?i:code-block|sourcecode)::\s*(?i:python|py|python3|py3)$",
             )
@@ -1320,7 +1320,7 @@ impl<'src> CodeExampleMarkdown<'src> {
     ///
     /// [fenced code block]: https://spec.commonmark.org/0.30/#fenced-code-blocks
     fn new(original: InputDocstringLine<'src>) -> Option<CodeExampleMarkdown<'src>> {
-        static FENCE_START: Lazy<Regex> = Lazy::new(|| {
+        static FENCE_START: LazyLock<Regex> = LazyLock::new(|| {
             Regex::new(
                 r"(?xm)
                 ^
diff --git a/crates/ruff_python_formatter/tests/normalizer.rs b/crates/ruff_python_formatter/tests/normalizer.rs
index b2cfc4dd6b08c..e5c84c5ab799e 100644
--- a/crates/ruff_python_formatter/tests/normalizer.rs
+++ b/crates/ruff_python_formatter/tests/normalizer.rs
@@ -1,6 +1,6 @@
+use std::sync::LazyLock;
 use {
     itertools::Either::{Left, Right},
-    once_cell::sync::Lazy,
     regex::Regex,
 };
 
@@ -60,7 +60,7 @@ impl Transformer for Normalizer {
     }
 
     fn visit_string_literal(&self, string_literal: &mut ast::StringLiteral) {
-        static STRIP_DOC_TESTS: Lazy<Regex> = Lazy::new(|| {
+        static STRIP_DOC_TESTS: LazyLock<Regex> = LazyLock::new(|| {
             Regex::new(
                 r"(?mx)
                     (
@@ -75,14 +75,14 @@ impl Transformer for Normalizer {
             )
             .unwrap()
         });
-        static STRIP_RST_BLOCKS: Lazy<Regex> = Lazy::new(|| {
+        static STRIP_RST_BLOCKS: LazyLock<Regex> = LazyLock::new(|| {
             // This is kind of unfortunate, but it's pretty tricky (likely
             // impossible) to detect a reStructuredText block with a simple
             // regex. So we just look for the start of a block and remove
             // everything after it. Talk about a hammer.
             Regex::new(r"::(?s:.*)").unwrap()
         });
-        static STRIP_MARKDOWN_BLOCKS: Lazy<Regex> = Lazy::new(|| {
+        static STRIP_MARKDOWN_BLOCKS: LazyLock<Regex> = LazyLock::new(|| {
             // This covers more than valid Markdown blocks, but that's OK.
             Regex::new(r"(```|~~~)\p{any}*(```|~~~|$)").unwrap()
         });
diff --git a/crates/ruff_source_file/Cargo.toml b/crates/ruff_source_file/Cargo.toml
index b57c2eb638bc9..0f82f37169ee8 100644
--- a/crates/ruff_source_file/Cargo.toml
+++ b/crates/ruff_source_file/Cargo.toml
@@ -16,7 +16,6 @@ license = { workspace = true }
 ruff_text_size = { workspace = true }
 
 memchr = { workspace = true }
-once_cell = { workspace = true }
 serde = { workspace = true, optional = true }
 
 [dev-dependencies]
diff --git a/crates/ruff_source_file/src/lib.rs b/crates/ruff_source_file/src/lib.rs
index 078c50cdc21e8..a0de92b1c14a0 100644
--- a/crates/ruff_source_file/src/lib.rs
+++ b/crates/ruff_source_file/src/lib.rs
@@ -1,6 +1,6 @@
 use std::cmp::Ordering;
 use std::fmt::{Debug, Display, Formatter};
-use std::sync::Arc;
+use std::sync::{Arc, OnceLock};
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -134,9 +134,9 @@ impl SourceFileBuilder {
     /// Consumes `self` and returns the [`SourceFile`].
     pub fn finish(self) -> SourceFile {
         let index = if let Some(index) = self.index {
-            once_cell::sync::OnceCell::with_value(index)
+            OnceLock::from(index)
         } else {
-            once_cell::sync::OnceCell::new()
+            OnceLock::new()
         };
 
         SourceFile {
@@ -218,7 +218,7 @@ impl Ord for SourceFile {
 struct SourceFileInner {
     name: Box<str>,
     code: Box<str>,
-    line_index: once_cell::sync::OnceCell<LineIndex>,
+    line_index: OnceLock<LineIndex>,
 }
 
 impl PartialEq for SourceFileInner {
diff --git a/crates/ruff_source_file/src/locator.rs b/crates/ruff_source_file/src/locator.rs
index 30bd59d830fe4..f133377a9e195 100644
--- a/crates/ruff_source_file/src/locator.rs
+++ b/crates/ruff_source_file/src/locator.rs
@@ -1,10 +1,9 @@
 //! Struct used to efficiently slice source code at (row, column) Locations.
 
-use std::ops::Add;
-
 use memchr::{memchr2, memrchr2};
-use once_cell::unsync::OnceCell;
 use ruff_text_size::{Ranged, TextLen, TextRange, TextSize};
+use std::cell::OnceCell;
+use std::ops::Add;
 
 use crate::newlines::find_newline;
 use crate::{LineIndex, OneIndexed, SourceCode, SourceLocation};
@@ -23,10 +22,10 @@ impl<'a> Locator<'a> {
         }
     }
 
-    pub const fn with_index(contents: &'a str, index: LineIndex) -> Self {
+    pub fn with_index(contents: &'a str, index: LineIndex) -> Self {
         Self {
             contents,
-            index: OnceCell::with_value(index),
+            index: OnceCell::from(index),
         }
     }