diff --git a/example_usage/lib/library_source.g.dart b/example_usage/lib/library_source.g.dart
index 482ec38e..26bcdcad 100644
--- a/example_usage/lib/library_source.g.dart
+++ b/example_usage/lib/library_source.g.dart
@@ -1,4 +1,5 @@
 // GENERATED CODE - DO NOT MODIFY BY HAND
+// dart format width=80
 
 // ignore_for_file: lint_a, lint_b
 
diff --git a/example_usage/lib/library_source.info.dart b/example_usage/lib/library_source.info.dart
index 736e6882..99b7457e 100644
--- a/example_usage/lib/library_source.info.dart
+++ b/example_usage/lib/library_source.info.dart
@@ -1,4 +1,5 @@
 // GENERATED CODE - DO NOT MODIFY BY HAND
+// dart format width=80
 
 // **************************************************************************
 // MemberCountLibraryGenerator
diff --git a/source_gen/CHANGELOG.md b/source_gen/CHANGELOG.md
index 8a903398..f21265b3 100644
--- a/source_gen/CHANGELOG.md
+++ b/source_gen/CHANGELOG.md
@@ -10,7 +10,10 @@
 - Support all the glob quotes.
 - Require `analyzer: ^6.9.0`
 - Require Dart 3.6.0-270.0.dev
-- `LibraryBuilder`, `PartBuilder`, and `SharedPartBuilder` now take an optional `writeDescriptions` boolean. When set to `false`, headers and generator descriptions for the files will not be included in the builder output.
+- `LibraryBuilder`, `PartBuilder`, and `SharedPartBuilder` now take an optional
+  `writeDescriptions` boolean. When set to `false`, headers and generator
+  descriptions for the files will not be included in the builder output.
+- Include `//dart format width=80` comments in generated Dart unit files.
 
 ## 1.5.0
 
diff --git a/source_gen/lib/builder.dart b/source_gen/lib/builder.dart
index 9daadb0a..e33bd4c0 100644
--- a/source_gen/lib/builder.dart
+++ b/source_gen/lib/builder.dart
@@ -143,6 +143,7 @@ class CombiningBuilder implements Builder {
 
     final output = '''
 $defaultFileHeader
+$dartFormatWidth
 ${languageOverrideForLibrary(inputLibrary)}$ignoreForFile$preamble
 part of '$partOfUri';
 
diff --git a/source_gen/lib/src/builder.dart b/source_gen/lib/src/builder.dart
index 13df806c..8945e107 100644
--- a/source_gen/lib/src/builder.dart
+++ b/source_gen/lib/src/builder.dart
@@ -134,6 +134,7 @@ class _Builder extends Builder {
 
       if (this is PartBuilder) {
         contentBuffer
+          ..writeln(dartFormatWidth)
           ..write(languageOverrideForLibrary(library))
           ..writeln('part of \'$partOfUri\';');
         final part = computePartUrl(buildStep.inputId, outputId);
@@ -155,6 +156,8 @@ class _Builder extends Builder {
         // For shared-part builders, `part` statements will be checked by the
         // combining build step.
       }
+    } else {
+      contentBuffer.writeln(dartFormatWidth);
     }
 
     for (var item in generatedOutputs) {
@@ -423,3 +426,7 @@ String languageOverrideForLibrary(LibraryElement library) {
       ? ''
       : '// @dart=${override.major}.${override.minor}\n';
 }
+
+/// A comment configuring `dart_style` to use the default code width so no
+/// configuration discovery is required.
+const dartFormatWidth = '// dart format width=80';
diff --git a/source_gen/test/builder_test.dart b/source_gen/test/builder_test.dart
index d6a6b76b..2d6bb8b9 100644
--- a/source_gen/test/builder_test.dart
+++ b/source_gen/test/builder_test.dart
@@ -11,6 +11,7 @@ import 'package:build/build.dart';
 import 'package:build_test/build_test.dart';
 import 'package:source_gen/builder.dart';
 import 'package:source_gen/source_gen.dart';
+import 'package:source_gen/src/builder.dart';
 import 'package:test/test.dart';
 
 import 'src/comment_generator.dart';
@@ -65,8 +66,9 @@ void main() {
       srcs,
       generateFor: {'$_pkgName|lib/test_lib.dart'},
       outputs: {
-        '$_pkgName|lib/test_lib.g.dart':
-            decodedMatches(startsWith('$_customHeader\n\n// ***')),
+        '$_pkgName|lib/test_lib.g.dart': decodedMatches(
+          startsWith('$_customHeader\n$dartFormatWidth\n\n// ***'),
+        ),
       },
     );
   });
@@ -79,7 +81,8 @@ void main() {
       srcs,
       generateFor: {'$_pkgName|lib/test_lib.dart'},
       outputs: {
-        '$_pkgName|lib/test_lib.g.dart': decodedMatches(startsWith('// ***')),
+        '$_pkgName|lib/test_lib.g.dart':
+            decodedMatches(startsWith('$dartFormatWidth\n\n// ***')),
       },
     );
   });
@@ -96,6 +99,7 @@ void main() {
     );
 
     const expected = '''
+$dartFormatWidth
 // Code for "class Person"
 // Code for "class Customer"
 ''';
@@ -312,8 +316,9 @@ void main() {
         {'$_pkgName|lib/a.dart': 'library a; part "a.foo.dart";'},
         generateFor: {'$_pkgName|lib/a.dart'},
         outputs: {
-          '$_pkgName|lib/a.foo.dart':
-              decodedMatches(startsWith('$_customHeader\n\npart of')),
+          '$_pkgName|lib/a.foo.dart': decodedMatches(
+            startsWith('$_customHeader\n\n$dartFormatWidth\npart of'),
+          ),
         },
       );
     });
@@ -328,7 +333,8 @@ void main() {
         {'$_pkgName|lib/a.dart': 'library a; part "a.foo.dart";'},
         generateFor: {'$_pkgName|lib/a.dart'},
         outputs: {
-          '$_pkgName|lib/a.foo.dart': decodedMatches(startsWith('part of')),
+          '$_pkgName|lib/a.foo.dart':
+              decodedMatches(startsWith('$dartFormatWidth\npart of')),
         },
       );
     });
@@ -341,13 +347,16 @@ void main() {
           header: '',
         ),
         {
-          '$_pkgName|lib/a.dart': '''// @dart=2.12
+          '$_pkgName|lib/a.dart': '''
+$dartFormatWidth
+// @dart=2.12
 part "a.foo.dart";''',
         },
         generateFor: {'$_pkgName|lib/a.dart'},
         outputs: {
-          '$_pkgName|lib/a.foo.dart':
-              decodedMatches(startsWith('// @dart=2.12\n')),
+          '$_pkgName|lib/a.foo.dart': decodedMatches(
+            startsWith('$dartFormatWidth\n// @dart=2.12\n'),
+          ),
         },
       );
     });
@@ -390,8 +399,9 @@ part "a.foo.dart";''',
           },
         );
         expect(logs, [
-          'generated/test_lib.foo.dart must be included as a part directive in the input '
-              'library with:\n    part \'generated/test_lib.foo.dart\';'
+          'generated/test_lib.foo.dart must be included as a '
+              'part directive in the input library with:\n'
+              '    part \'generated/test_lib.foo.dart\';'
         ]);
       });
 
@@ -411,8 +421,9 @@ part "a.foo.dart";''',
           {'$_pkgName|lib/a.dart': 'part "generated/a.foo.dart";'},
           generateFor: {'$_pkgName|lib/a.dart'},
           outputs: {
-            '$_pkgName|lib/generated/a.foo.dart':
-                decodedMatches(startsWith("part of '../a.dart';")),
+            '$_pkgName|lib/generated/a.foo.dart': decodedMatches(
+              startsWith("$dartFormatWidth\npart of '../a.dart';"),
+            ),
           },
         );
       });
@@ -559,6 +570,7 @@ part "a.foo.dart";''',
         const CombiningBuilder(),
         {
           '$_pkgName|lib/a.dart': '''
+$dartFormatWidth
 // @dart=2.12
 library a;
 part "a.g.dart";
@@ -570,6 +582,7 @@ part "a.g.dart";
           '$_pkgName|lib/a.g.dart': decodedMatches(
             '''
 // GENERATED CODE - DO NOT MODIFY BY HAND
+$dartFormatWidth
 // @dart=2.12
 
 part of 'a.dart';
@@ -1056,8 +1069,10 @@ const _testLibContentSyntaxError = r'''
 final int foo = 42
 ''';
 
-const _testGenPartContent = r'''// GENERATED CODE - DO NOT MODIFY BY HAND
+const _testGenPartContent = r'''
+// GENERATED CODE - DO NOT MODIFY BY HAND
 
+// dart format width=80
 part of 'test_lib.dart';
 
 // **************************************************************************
@@ -1068,9 +1083,10 @@ part of 'test_lib.dart';
 // Code for "class Customer"
 ''';
 
-const _testGenPartContentForLibrary =
-    r'''// GENERATED CODE - DO NOT MODIFY BY HAND
+const _testGenPartContentForLibrary = r'''
+// GENERATED CODE - DO NOT MODIFY BY HAND
 
+// dart format width=80
 part of 'test_lib.dart';
 
 // **************************************************************************
@@ -1080,7 +1096,9 @@ part of 'test_lib.dart';
 // Code for "test_lib"
 ''';
 
-const _testGenStandaloneContent = r'''// GENERATED CODE - DO NOT MODIFY BY HAND
+const _testGenStandaloneContent = r'''
+// GENERATED CODE - DO NOT MODIFY BY HAND
+// dart format width=80
 
 // **************************************************************************
 // CommentGenerator
@@ -1090,9 +1108,10 @@ const _testGenStandaloneContent = r'''// GENERATED CODE - DO NOT MODIFY BY HAND
 // Code for "class Customer"
 ''';
 
-const _testGenPartContentForClassesAndLibrary =
-    r'''// GENERATED CODE - DO NOT MODIFY BY HAND
+const _testGenPartContentForClassesAndLibrary = r'''
+// GENERATED CODE - DO NOT MODIFY BY HAND
 
+// dart format width=80
 part of 'test_lib.dart';
 
 // **************************************************************************
@@ -1104,8 +1123,10 @@ part of 'test_lib.dart';
 // Code for "class Customer"
 ''';
 
-const _testGenNoLibrary = r'''// GENERATED CODE - DO NOT MODIFY BY HAND
+const _testGenNoLibrary = r'''
+// GENERATED CODE - DO NOT MODIFY BY HAND
 
+// dart format width=80
 part of 'test_lib.dart';
 
 // **************************************************************************
@@ -1116,8 +1137,10 @@ part of 'test_lib.dart';
 // Code for "class Customer"
 ''';
 
-const _whitespaceTrimmed = r'''// GENERATED CODE - DO NOT MODIFY BY HAND
+const _whitespaceTrimmed = r'''
+// GENERATED CODE - DO NOT MODIFY BY HAND
 
+// dart format width=80
 part of 'test_lib.dart';
 
 // **************************************************************************
diff --git a/source_gen/test/generator_for_annotation_test.dart b/source_gen/test/generator_for_annotation_test.dart
index 391285ec..abd426a1 100644
--- a/source_gen/test/generator_for_annotation_test.dart
+++ b/source_gen/test/generator_for_annotation_test.dart
@@ -12,6 +12,7 @@ import 'package:analyzer/dart/element/element.dart';
 import 'package:build/build.dart';
 import 'package:build_test/build_test.dart';
 import 'package:source_gen/source_gen.dart';
+import 'package:source_gen/src/builder.dart';
 import 'package:test/test.dart';
 
 void main() {
@@ -44,6 +45,7 @@ void main() {
       outputs: {
         'a|lib/file.g.dart': r'''
 // GENERATED CODE - DO NOT MODIFY BY HAND
+// dart format width=80
 
 // **************************************************************************
 // Generator: Repeating
@@ -128,6 +130,7 @@ void main() {
       outputs: {
         'a|lib/file.g.dart': '''
 // GENERATED CODE - DO NOT MODIFY BY HAND
+$dartFormatWidth
 
 // **************************************************************************
 // Generator: Deprecated
@@ -164,6 +167,7 @@ void main() {
       outputs: {
         'a|lib/file.g.dart': '''
 // GENERATED CODE - DO NOT MODIFY BY HAND
+$dartFormatWidth
 
 // **************************************************************************
 // Generator: Deprecated