diff --git a/CHANGELOG.md b/CHANGELOG.md
index f1a014ef..e32dd763 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,10 @@
 <!-- When submitting a PR for a feature, add the appropriate prerelease heading here
 and fill in the contents as you go. This simplifies later release management. -->
 
+## 2.5.0
+
+- Add `HM.Files.PatternSlugMatchesFilename` sniff verifying that a theme pattern file's `Slug:` header matches its filename
+
 ## 2.4.0
 
 - Add `HM.Functions.RegisterBlockTypePath` sniff recommending `register_block_type_from_metadata()` when a file path is passed to `register_block_type()`
diff --git a/HM/Sniffs/Files/PatternSlugMatchesFilenameSniff.php b/HM/Sniffs/Files/PatternSlugMatchesFilenameSniff.php
new file mode 100644
index 00000000..76d72e15
--- /dev/null
+++ b/HM/Sniffs/Files/PatternSlugMatchesFilenameSniff.php
@@ -0,0 +1,62 @@
+<?php
+/**
+ * Sniff verifying that theme pattern slugs match their filenames.
+ */
+
+namespace HM\Sniffs\Files;
+
+use PHP_CodeSniffer\Files\File;
+use PHP_CodeSniffer\Sniffs\Sniff;
+
+/**
+ * Flags theme pattern files whose Slug: header does not end with the file's basename.
+ *
+ * A pattern with `Slug: my-theme/hero-banner` must live in `hero-banner.php`.
+ */
+class PatternSlugMatchesFilenameSniff implements Sniff {
+
+	/**
+	 * Register for the open tag so the check runs once per file.
+	 *
+	 * @return array<int|string>
+	 */
+	public function register() : array {
+		return [ T_OPEN_TAG ];
+	}
+
+	/**
+	 * Compare the trailing segment of the pattern's Slug header to the filename.
+	 *
+	 * @param File $phpcs_file The file being scanned.
+	 * @param int  $stack_ptr  Position of the open tag.
+	 * @return int Pointer past the end of the file, so the sniff runs only once.
+	 */
+	public function process( File $phpcs_file, $stack_ptr ) {
+		if ( ! preg_match( '#/themes/[^/]+/patterns/([^/]+)\.php$#', $phpcs_file->getFilename(), $matches ) ) {
+			return $phpcs_file->numTokens;
+		}
+		$filename = $matches[1];
+
+		foreach ( $phpcs_file->getTokens() as $ptr => $token ) {
+			if ( T_DOC_COMMENT_STRING !== $token['code'] ) {
+				continue;
+			}
+			if ( ! preg_match( '#^Slug:\s*(\S+)#', trim( $token['content'] ), $slug_match ) ) {
+				continue;
+			}
+
+			$slug = $slug_match[1];
+			if ( basename( $slug ) !== $filename ) {
+				$phpcs_file->addError(
+					'Pattern slug "%s" does not match the filename; expected the file to be named "%s.php".',
+					$ptr,
+					'SlugMismatch',
+					[ $slug, basename( $slug ) ]
+				);
+			}
+			break;
+		}
+
+		return $phpcs_file->numTokens;
+	}
+}
diff --git a/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest.php b/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest.php
new file mode 100644
index 00000000..849f0b15
--- /dev/null
+++ b/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest.php
@@ -0,0 +1,68 @@
+<?php
+
+namespace HM\Tests\Files;
+
+use RecursiveDirectoryIterator;
+use RecursiveIteratorIterator;
+use PHP_CodeSniffer\Tests\Standards\AbstractSniffUnitTest;
+
+/**
+ * Class PatternSlugMatchesFilenameUnitTest
+ *
+ * @group hm-sniffs
+ */
+class PatternSlugMatchesFilenameUnitTest extends AbstractSniffUnitTest {
+	/**
+	 * Get files to test against.
+	 *
+	 * Overridden from base to recurse through the fixture directory, since
+	 * the sniff only applies to files within a theme's patterns directory.
+	 */
+	protected function getTestFiles( $test_base_dir ) {
+		$test_base_dir = rtrim( $test_base_dir, '.' );
+		$test_files = [];
+
+		$di = new RecursiveIteratorIterator(
+			new RecursiveDirectoryIterator( $test_base_dir )
+		);
+
+		foreach ( $di as $file ) {
+			if ( ! $file->isFile() ) {
+				continue;
+			}
+
+			$test_files[] = $file->getPathname();
+		}
+
+		// Put them in order.
+		sort( $test_files );
+
+		return $test_files;
+	}
+
+	/**
+	 * Returns the lines where errors should occur.
+	 *
+	 * @return array <int line number> => <int number of errors>
+	 */
+	public function getErrorList() {
+		$file = func_get_arg( 0 );
+		$fail = [
+			'renamed-pattern.php' => [
+				4 => 1,
+			],
+		];
+
+		return $fail[ $file ] ?? [];
+	}
+
+	/**
+	 * Returns the lines where warnings should occur.
+	 *
+	 * @return array <int line number> => <int number of warnings>
+	 */
+	public function getWarningList() {
+		return [];
+	}
+
+}
diff --git a/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/functions.php b/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/functions.php
new file mode 100644
index 00000000..1d01a7b5
--- /dev/null
+++ b/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/functions.php
@@ -0,0 +1,7 @@
+<?php
+/**
+ * Title: Not a pattern
+ * Slug: my-theme/some-other-slug
+ *
+ * Files outside a patterns directory are ignored even if they have a Slug header.
+ */
diff --git a/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/patterns/hero-banner.php b/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/patterns/hero-banner.php
new file mode 100644
index 00000000..5052170b
--- /dev/null
+++ b/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/patterns/hero-banner.php
@@ -0,0 +1,8 @@
+<?php
+/**
+ * Title: Hero Banner
+ * Slug: my-theme/hero-banner
+ * Categories: banner
+ */
+?>
+<!-- wp:paragraph --><p>Hero banner content.</p><!-- /wp:paragraph -->
diff --git a/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/patterns/no-slug.php b/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/patterns/no-slug.php
new file mode 100644
index 00000000..751c938e
--- /dev/null
+++ b/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/patterns/no-slug.php
@@ -0,0 +1,6 @@
+<?php
+/**
+ * A pattern-directory file without a Slug header is not flagged.
+ */
+?>
+<!-- wp:paragraph --><p>No slug here.</p><!-- /wp:paragraph -->
diff --git a/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/patterns/renamed-pattern.php b/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/patterns/renamed-pattern.php
new file mode 100644
index 00000000..fc138385
--- /dev/null
+++ b/HM/Tests/Files/PatternSlugMatchesFilenameUnitTest/themes/my-theme/patterns/renamed-pattern.php
@@ -0,0 +1,8 @@
+<?php
+/**
+ * Title: Hero Banner
+ * Slug: my-theme/hero-banner
+ * Categories: banner
+ */
+?>
+<!-- wp:paragraph --><p>The slug above does not match this filename.</p><!-- /wp:paragraph -->