diff --git a/Cargo.lock b/Cargo.lock
index cc673ff26235c..12f1c26b1153e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2033,6 +2033,7 @@ dependencies = [
  "textwrap",
  "thiserror",
  "toml",
+ "typed-arena",
  "unicode-width",
 ]
 
@@ -2919,6 +2920,12 @@ dependencies = [
  "static_assertions",
 ]
 
+[[package]]
+name = "typed-arena"
+version = "2.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6af6ae20167a9ece4bcb41af5b80f8a1f1df981f6391189ce00fd257af04126a"
+
 [[package]]
 name = "typenum"
 version = "1.16.0"
diff --git a/crates/ruff/Cargo.toml b/crates/ruff/Cargo.toml
index 13d8b892e619d..d9522b738c21f 100644
--- a/crates/ruff/Cargo.toml
+++ b/crates/ruff/Cargo.toml
@@ -66,7 +66,8 @@ strum_macros = { workspace = true }
 textwrap = { workspace = true }
 thiserror = { version = "1.0.38" }
 toml = { workspace = true }
-unicode-width = "0.1.10"
+typed-arena = { version = "2.0.2" }
+unicode-width = {version ="0.1.10"}
 
 [dev-dependencies]
 insta = { workspace = true, features = ["yaml", "redactions"] }
diff --git a/crates/ruff/resources/test/fixtures/pyflakes/F401_11.py b/crates/ruff/resources/test/fixtures/pyflakes/F401_11.py
new file mode 100644
index 0000000000000..a74c3579caa0e
--- /dev/null
+++ b/crates/ruff/resources/test/fixtures/pyflakes/F401_11.py
@@ -0,0 +1,7 @@
+"""Test: parsing of nested string annotations."""
+
+from typing import List
+from pathlib import Path, PurePath
+
+
+x: """List['Path']""" = []
diff --git a/crates/ruff/resources/test/fixtures/pyupgrade/UP006.py b/crates/ruff/resources/test/fixtures/pyupgrade/UP006.py
index 0668569a55a1d..75a369bfb9254 100644
--- a/crates/ruff/resources/test/fixtures/pyupgrade/UP006.py
+++ b/crates/ruff/resources/test/fixtures/pyupgrade/UP006.py
@@ -44,3 +44,15 @@ def f(x: """List[str]""") -> None:
 
 def f(x: "Li" "st[str]") -> None:
     ...
+
+
+def f(x: "List['List[str]']") -> None:
+    ...
+
+
+def f(x: "List['Li' 'st[str]']") -> None:
+    ...
+
+
+def f(x: "Li" "st['List[str]']") -> None:
+    ...
diff --git a/crates/ruff/src/checkers/ast/mod.rs b/crates/ruff/src/checkers/ast/mod.rs
index 80777b2a88960..9333ca16db310 100644
--- a/crates/ruff/src/checkers/ast/mod.rs
+++ b/crates/ruff/src/checkers/ast/mod.rs
@@ -4525,47 +4525,49 @@ impl<'a> Checker<'a> {
         }
     }
 
-    fn check_deferred_string_type_definitions(&mut self, allocator: &'a mut Vec<Expr>) {
-        let mut stacks = Vec::with_capacity(self.deferred.string_type_definitions.len());
-        self.deferred.string_type_definitions.reverse();
-        while let Some((range, value, (in_annotation, in_type_checking_block), deferral)) =
-            self.deferred.string_type_definitions.pop()
-        {
-            if let Ok((expr, kind)) = parse_type_annotation(value, range, self.locator) {
-                if in_annotation && self.ctx.annotations_future_enabled {
-                    if self.settings.rules.enabled(Rule::QuotedAnnotation) {
-                        pyupgrade::rules::quoted_annotation(self, value, range);
+    fn check_deferred_string_type_definitions(&mut self, allocator: &'a typed_arena::Arena<Expr>) {
+        let mut type_definitions = std::mem::take(&mut self.deferred.string_type_definitions);
+        loop {
+            for (range, value, (in_annotation, in_type_checking_block), (scopes, parents)) in
+                type_definitions.into_iter().rev()
+            {
+                if let Ok((expr, kind)) = parse_type_annotation(value, range, self.locator) {
+                    if in_annotation && self.ctx.annotations_future_enabled {
+                        if self.settings.rules.enabled(Rule::QuotedAnnotation) {
+                            pyupgrade::rules::quoted_annotation(self, value, range);
+                        }
+                    }
+
+                    let expr = allocator.alloc(expr);
+
+                    self.ctx.scope_stack = scopes;
+                    self.ctx.parents = parents;
+                    self.ctx.in_annotation = in_annotation;
+                    self.ctx.in_type_checking_block = in_type_checking_block;
+                    self.ctx.in_type_definition = true;
+                    self.ctx.in_deferred_string_type_definition = Some(kind);
+                    self.visit_expr(expr);
+                    self.ctx.in_deferred_string_type_definition = None;
+                    self.ctx.in_type_definition = false;
+                } else {
+                    if self
+                        .settings
+                        .rules
+                        .enabled(Rule::ForwardAnnotationSyntaxError)
+                    {
+                        self.diagnostics.push(Diagnostic::new(
+                            pyflakes::rules::ForwardAnnotationSyntaxError {
+                                body: value.to_string(),
+                            },
+                            range,
+                        ));
                     }
-                }
-                allocator.push(expr);
-                stacks.push((kind, (in_annotation, in_type_checking_block), deferral));
-            } else {
-                if self
-                    .settings
-                    .rules
-                    .enabled(Rule::ForwardAnnotationSyntaxError)
-                {
-                    self.diagnostics.push(Diagnostic::new(
-                        pyflakes::rules::ForwardAnnotationSyntaxError {
-                            body: value.to_string(),
-                        },
-                        range,
-                    ));
                 }
             }
-        }
-        for (expr, (kind, (in_annotation, in_type_checking_block), (scopes, parents))) in
-            allocator.iter().zip(stacks)
-        {
-            self.ctx.scope_stack = scopes;
-            self.ctx.parents = parents;
-            self.ctx.in_annotation = in_annotation;
-            self.ctx.in_type_checking_block = in_type_checking_block;
-            self.ctx.in_type_definition = true;
-            self.ctx.in_deferred_string_type_definition = Some(kind);
-            self.visit_expr(expr);
-            self.ctx.in_deferred_string_type_definition = None;
-            self.ctx.in_type_definition = false;
+            if self.deferred.string_type_definitions.is_empty() {
+                break;
+            }
+            type_definitions = std::mem::take(&mut self.deferred.string_type_definitions);
         }
     }
 
@@ -5394,8 +5396,8 @@ pub fn check_ast(
     checker.check_deferred_functions();
     checker.check_deferred_lambdas();
     checker.check_deferred_type_definitions();
-    let mut allocator = vec![];
-    checker.check_deferred_string_type_definitions(&mut allocator);
+    let allocator = typed_arena::Arena::new();
+    checker.check_deferred_string_type_definitions(&allocator);
     checker.check_deferred_assignments();
     checker.check_deferred_for_loops();
 
diff --git a/crates/ruff/src/rules/pyflakes/mod.rs b/crates/ruff/src/rules/pyflakes/mod.rs
index 0e4fc33e76f12..d063cf52e58dc 100644
--- a/crates/ruff/src/rules/pyflakes/mod.rs
+++ b/crates/ruff/src/rules/pyflakes/mod.rs
@@ -34,6 +34,7 @@ mod tests {
     #[test_case(Rule::UnusedImport, Path::new("F401_8.py"); "F401_8")]
     #[test_case(Rule::UnusedImport, Path::new("F401_9.py"); "F401_9")]
     #[test_case(Rule::UnusedImport, Path::new("F401_10.py"); "F401_10")]
+    #[test_case(Rule::UnusedImport, Path::new("F401_11.py"); "F401_11")]
     #[test_case(Rule::ImportShadowedByLoopVar, Path::new("F402.py"); "F402")]
     #[test_case(Rule::UndefinedLocalWithImportStar, Path::new("F403.py"); "F403")]
     #[test_case(Rule::LateFutureImport, Path::new("F404.py"); "F404")]
diff --git a/crates/ruff/src/rules/pyflakes/snapshots/ruff__rules__pyflakes__tests__F401_F401_11.py.snap b/crates/ruff/src/rules/pyflakes/snapshots/ruff__rules__pyflakes__tests__F401_F401_11.py.snap
new file mode 100644
index 0000000000000..a5c6b1c42ea9a
--- /dev/null
+++ b/crates/ruff/src/rules/pyflakes/snapshots/ruff__rules__pyflakes__tests__F401_F401_11.py.snap
@@ -0,0 +1,25 @@
+---
+source: crates/ruff/src/rules/pyflakes/mod.rs
+expression: diagnostics
+---
+- kind:
+    name: UnusedImport
+    body: "`pathlib.PurePath` imported but unused"
+    suggestion: "Remove unused import: `pathlib.PurePath`"
+    fixable: true
+  location:
+    row: 4
+    column: 26
+  end_location:
+    row: 4
+    column: 34
+  fix:
+    content: from pathlib import Path
+    location:
+      row: 4
+      column: 0
+    end_location:
+      row: 4
+      column: 34
+  parent: ~
+
diff --git a/crates/ruff/src/rules/pyupgrade/snapshots/ruff__rules__pyupgrade__tests__UP006.py.snap b/crates/ruff/src/rules/pyupgrade/snapshots/ruff__rules__pyupgrade__tests__UP006.py.snap
index 521221c78ea2b..9c24e1b513973 100644
--- a/crates/ruff/src/rules/pyupgrade/snapshots/ruff__rules__pyupgrade__tests__UP006.py.snap
+++ b/crates/ruff/src/rules/pyupgrade/snapshots/ruff__rules__pyupgrade__tests__UP006.py.snap
@@ -175,4 +175,103 @@ expression: diagnostics
     column: 23
   fix: ~
   parent: ~
+- kind:
+    name: NonPEP585Annotation
+    body: "Use `list` instead of `List` for type annotations"
+    suggestion: "Replace `List` with `list`"
+    fixable: true
+  location:
+    row: 49
+    column: 10
+  end_location:
+    row: 49
+    column: 14
+  fix:
+    content: list
+    location:
+      row: 49
+      column: 10
+    end_location:
+      row: 49
+      column: 14
+  parent: ~
+- kind:
+    name: NonPEP585Annotation
+    body: "Use `list` instead of `List` for type annotations"
+    suggestion: "Replace `List` with `list`"
+    fixable: true
+  location:
+    row: 49
+    column: 16
+  end_location:
+    row: 49
+    column: 20
+  fix:
+    content: list
+    location:
+      row: 49
+      column: 16
+    end_location:
+      row: 49
+      column: 20
+  parent: ~
+- kind:
+    name: NonPEP585Annotation
+    body: "Use `list` instead of `List` for type annotations"
+    suggestion: "Replace `List` with `list`"
+    fixable: true
+  location:
+    row: 53
+    column: 10
+  end_location:
+    row: 53
+    column: 14
+  fix:
+    content: list
+    location:
+      row: 53
+      column: 10
+    end_location:
+      row: 53
+      column: 14
+  parent: ~
+- kind:
+    name: NonPEP585Annotation
+    body: "Use `list` instead of `List` for type annotations"
+    suggestion: ~
+    fixable: false
+  location:
+    row: 53
+    column: 15
+  end_location:
+    row: 53
+    column: 29
+  fix: ~
+  parent: ~
+- kind:
+    name: NonPEP585Annotation
+    body: "Use `list` instead of `List` for type annotations"
+    suggestion: ~
+    fixable: false
+  location:
+    row: 57
+    column: 9
+  end_location:
+    row: 57
+    column: 31
+  fix: ~
+  parent: ~
+- kind:
+    name: NonPEP585Annotation
+    body: "Use `list` instead of `List` for type annotations"
+    suggestion: ~
+    fixable: false
+  location:
+    row: 57
+    column: 9
+  end_location:
+    row: 57
+    column: 31
+  fix: ~
+  parent: ~