diff --git a/docbookcs.xml.dist b/docbookcs.xml.dist
index 51ee17a..bed6138 100644
--- a/docbookcs.xml.dist
+++ b/docbookcs.xml.dist
@@ -16,6 +16,7 @@
         </sniff>
 
         <sniff class="DocbookCS\Sniff\AttributeOrderSniff" />
+        <sniff class="DocbookCS\Sniff\FileEmptyLastLineSniffer" />
     </sniffs>
 
     <paths>
diff --git a/src/Fix/Fixer/FileEmptyLastLineFixer.php b/src/Fix/Fixer/FileEmptyLastLineFixer.php
new file mode 100644
index 0000000..bfbaa13
--- /dev/null
+++ b/src/Fix/Fixer/FileEmptyLastLineFixer.php
@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DocbookCS\Fix\Fixer;
+
+use DocbookCS\Fix\Fix;
+use DocbookCS\Fix\FixerException;
+use DocbookCS\Violation\Violation;
+
+final class FileEmptyLastLineFixer implements Fixer
+{
+    private const string LINE_ENDINGS_PATTERN = '/^[\r\n]+$/D';
+    private const string UNTERMINATED_LINE_PATTERN = '/^[^\r\n]+$/D';
+
+    /** @throws FixerException */
+    public function process(Violation $violation): Fix
+    {
+        $affectedRange = $violation->rangeOne();
+        $affectedContent = $affectedRange->content;
+
+        if ($affectedContent === null) {
+            throw FixerException::cannotFixMissingContent();
+        }
+
+        if (preg_match(self::LINE_ENDINGS_PATTERN, $affectedContent)) {
+            return Fix::fromViolationAndRange($violation, $affectedRange, "\n");
+        }
+
+        if (!preg_match(self::UNTERMINATED_LINE_PATTERN, $affectedContent)) {
+            throw FixerException::cannotFixInvalidContent($violation);
+        }
+
+        return Fix::fromViolationAndRange(
+            $violation,
+            $affectedRange,
+            $affectedContent . "\n",
+        );
+    }
+}
diff --git a/src/Sniff/FileEmptyLastLineSniffer.php b/src/Sniff/FileEmptyLastLineSniffer.php
new file mode 100644
index 0000000..6d99be2
--- /dev/null
+++ b/src/Sniff/FileEmptyLastLineSniffer.php
@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DocbookCS\Sniff;
+
+use DocbookCS\Fix\Fixer\FileEmptyLastLineFixer;
+use DocbookCS\Source\File;
+use DocbookCS\Violation\SourceRange;
+
+final class FileEmptyLastLineSniffer extends AbstractSniff implements Fixable
+{
+    private const string FILE_END_PATTERN = '/(?:[\r\n]+|[^\r\n]*)\z/';
+    private const string REPORTING_MESSAGE = 'File must end with exactly one empty (LF) line.';
+
+    public static function getCode(): string
+    {
+        return 'DocbookCS.FileEmptyLastLine';
+    }
+
+    public static function getFixerClassName(): string
+    {
+        return FileEmptyLastLineFixer::class;
+    }
+
+    /**
+     * @throws \InvalidArgumentException if a generated source range is inconsistent
+     * @throws \OutOfBoundsException if a generated source range lies outside the source
+     * @throws SniffException if the file ending cannot be identified
+     */
+    public function process(\DOMDocument $document, File $file): array
+    {
+        if (preg_match(self::FILE_END_PATTERN, $file->content, $matches, PREG_OFFSET_CAPTURE) !== 1) {
+            throw SniffException::cannotIdentifyFileEnding();
+        }
+
+        [$affectedContent, $beginOffset] = $matches[0];
+
+        if ($affectedContent === "\n") {
+            return [];
+        }
+
+        return [
+            $this->createViolation(
+                $file->path,
+                self::REPORTING_MESSAGE,
+                [SourceRange::fromFile($file, $beginOffset, strlen($file->content))],
+            ),
+        ];
+    }
+}
diff --git a/src/Sniff/SniffException.php b/src/Sniff/SniffException.php
new file mode 100644
index 0000000..4dc42eb
--- /dev/null
+++ b/src/Sniff/SniffException.php
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DocbookCS\Sniff;
+
+final class SniffException extends \RuntimeException
+{
+    public static function cannotIdentifyFileEnding(): self
+    {
+        return new self('Cannot identify file ending.');
+    }
+}
diff --git a/tests/Unit/Fix/FileEmptyLastLineFixerTest.php b/tests/Unit/Fix/FileEmptyLastLineFixerTest.php
new file mode 100644
index 0000000..24c4b35
--- /dev/null
+++ b/tests/Unit/Fix/FileEmptyLastLineFixerTest.php
@@ -0,0 +1,88 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DocbookCS\Tests\Unit\Fix;
+
+use DocbookCS\Fix\Fix;
+use DocbookCS\Fix\FixApplier;
+use DocbookCS\Fix\Fixer\FileEmptyLastLineFixer;
+use DocbookCS\Fix\FixPlan;
+use DocbookCS\Fix\FixResult;
+use DocbookCS\Sniff\FileEmptyLastLineSniffer;
+use DocbookCS\Source\File;
+use DocbookCS\Violation\SourceRange;
+use DocbookCS\Violation\Violation;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\Attributes\UsesClass;
+use PHPUnit\Framework\TestCase;
+
+#[
+    CoversClass(FileEmptyLastLineFixer::class),
+    CoversClass(FileEmptyLastLineSniffer::class),
+    CoversClass(Fix::class),
+    CoversClass(FixApplier::class),
+    CoversClass(FixResult::class),
+    //
+    UsesClass(File::class),
+    UsesClass(FixPlan::class),
+    UsesClass(SourceRange::class),
+    UsesClass(Violation::class),
+]
+final class FileEmptyLastLineFixerTest extends TestCase
+{
+    #[Test]
+    public function itTreatsTheCanonicalEndingAsANoOp(): void
+    {
+        $content = "<root/>\n";
+        $source = new File('file.xml', $content);
+        $range = new SourceRange(1, strlen($content) - 1, strlen($content), "\n");
+        $violation = new Violation(
+            FileEmptyLastLineSniffer::getCode(),
+            $source->path,
+            'violation.',
+            [$range],
+        );
+
+        $fix = new FileEmptyLastLineFixer()->process($violation);
+        $result = new FixApplier()->apply($source, [$fix]);
+
+        self::assertSame($content, $result->file->content);
+        self::assertSame(0, $result->applied);
+        self::assertSame(1, $result->skipped);
+    }
+
+    #[Test, DataProvider('nonCompliantEndings')]
+    public function itLeavesExactlyOneLfEmptyLastLine(string $content, string $expected): void
+    {
+        $source = new File('file.xml', $content);
+        $document = new \DOMDocument();
+        $document->loadXML($content);
+        $sniffer = new FileEmptyLastLineSniffer();
+        $violation = $sniffer->process($document, $source)[0];
+
+        $fix = new FileEmptyLastLineFixer()->process($violation);
+        $result = new FixApplier()->apply($source, [$fix]);
+
+        self::assertSame($expected, $result->file->content);
+        self::assertSame(1, $result->applied);
+        self::assertSame([], $sniffer->process($document, $result->file));
+    }
+
+    /** @return iterable<string, array{string, string}> */
+    public static function nonCompliantEndings(): iterable
+    {
+        yield 'missing ending' => ['<root/>', "<root/>\n"];
+        yield 'after line feed content' => ["<root>\n</root>", "<root>\n</root>\n"];
+        yield 'after carriage return and line feed content' => ["<root>\r\n</root>", "<root>\r\n</root>\n"];
+        yield 'after carriage return content' => ["<root>\r</root>", "<root>\r</root>\n"];
+        yield 'extra line feed' => ["<root/>\n\n", "<root/>\n"];
+        yield 'carriage return and line feed' => ["<root/>\r\n", "<root/>\n"];
+        yield 'carriage return' => ["<root/>\r", "<root/>\n"];
+        yield 'extra carriage return and line feed' => ["<root/>\r\n\r\n", "<root/>\n"];
+        yield 'extra carriage return' => ["<root/>\r\r", "<root/>\n"];
+        yield 'multiple mixed extra endings' => ["<root/>\r\n\n\r", "<root/>\n"];
+    }
+}
diff --git a/tests/Unit/Fix/FixerInputValidationTest.php b/tests/Unit/Fix/FixerInputValidationTest.php
index 7163752..e4c1608 100644
--- a/tests/Unit/Fix/FixerInputValidationTest.php
+++ b/tests/Unit/Fix/FixerInputValidationTest.php
@@ -6,6 +6,7 @@
 
 use DocbookCS\Fix\Fixer\AttributeOrderFixer;
 use DocbookCS\Fix\Fixer\ExceptionNameFixer;
+use DocbookCS\Fix\Fixer\FileEmptyLastLineFixer;
 use DocbookCS\Fix\Fixer\Fixer;
 use DocbookCS\Fix\Fixer\MixedIndentationFixer;
 use DocbookCS\Fix\Fixer\SimparaFixer;
@@ -22,6 +23,7 @@
 #[
     CoversClass(AttributeOrderFixer::class),
     CoversClass(ExceptionNameFixer::class),
+    CoversClass(FileEmptyLastLineFixer::class),
     CoversClass(FixerException::class),
     CoversClass(MixedIndentationFixer::class),
     CoversClass(SimparaFixer::class),
@@ -50,6 +52,7 @@ public static function missingContent(): iterable
             new SourceRange(1, 0, 9),
             new SourceRange(1, 10, 19),
         ]];
+        yield 'file empty last line' => [new FileEmptyLastLineFixer(), [new SourceRange(1, 0, 4)]];
         yield 'mixed indentation' => [new MixedIndentationFixer(), [new SourceRange(1, 0, 2)]];
         yield 'simpara' => [new SimparaFixer(), [
             new SourceRange(1, 0, 4),
@@ -77,6 +80,14 @@ public static function invalidContent(): iterable
             new SourceRange(1, 0, 5, 'class'),
             new SourceRange(1, 6, 11, 'class'),
         ]];
+        yield 'file empty last line with mixed content' => [
+            new FileEmptyLastLineFixer(),
+            [new SourceRange(1, 0, 9, "text\ntext")],
+        ];
+        yield 'file empty last line with empty range' => [
+            new FileEmptyLastLineFixer(),
+            [new SourceRange(1, 0, 0, '')],
+        ];
         yield 'mixed indentation' => [new MixedIndentationFixer(), [new SourceRange(1, 0, 2, '  ')]];
         yield 'simpara' => [new SimparaFixer(), [
             new SourceRange(1, 0, 4, 'span'),
diff --git a/tests/Unit/Fix/WhitespaceConcernFixersTest.php b/tests/Unit/Fix/WhitespaceConcernFixersTest.php
index 5067538..819b33f 100644
--- a/tests/Unit/Fix/WhitespaceConcernFixersTest.php
+++ b/tests/Unit/Fix/WhitespaceConcernFixersTest.php
@@ -7,9 +7,11 @@
 use DocbookCS\Fix\Fix;
 use DocbookCS\Fix\FixApplier;
 use DocbookCS\Fix\FixPlan;
+use DocbookCS\Fix\Fixer\FileEmptyLastLineFixer;
 use DocbookCS\Fix\Fixer\MixedIndentationFixer;
 use DocbookCS\Fix\Fixer\TrailingWhitespaceFixer;
 use DocbookCS\Fix\FixResult;
+use DocbookCS\Sniff\FileEmptyLastLineSniffer;
 use DocbookCS\Sniff\MixedIndentationSniff;
 use DocbookCS\Sniff\TrailingWhitespaceSniff;
 use DocbookCS\Source\File;
@@ -25,6 +27,8 @@
     CoversClass(Fix::class),
     CoversClass(FixApplier::class),
     CoversClass(FixResult::class),
+    CoversClass(FileEmptyLastLineFixer::class),
+    CoversClass(FileEmptyLastLineSniffer::class),
     CoversClass(MixedIndentationFixer::class),
     CoversClass(MixedIndentationSniff::class),
     CoversClass(TrailingWhitespaceFixer::class),
@@ -72,4 +76,25 @@ public function itFixesIndependentWhitespaceConcernsTogether(): void
         self::assertSame(3, $result->applied);
         self::assertSame(0, $result->skipped);
     }
+
+    #[Test]
+    public function itFixesTrailingWhitespaceAndTheFileEndingTogether(): void
+    {
+        $content = "<root/> \n\n";
+        $document = new \DOMDocument();
+        $document->loadXML($content);
+        $source = new File('file.xml', $content);
+
+        $trailingViolation = new TrailingWhitespaceSniff()->process($document, $source)[0];
+        $fileEndingViolation = new FileEmptyLastLineSniffer()->process($document, $source)[0];
+
+        $result = new FixApplier()->apply($source, [
+            new TrailingWhitespaceFixer()->process($trailingViolation),
+            new FileEmptyLastLineFixer()->process($fileEndingViolation),
+        ]);
+
+        self::assertSame("<root/>\n", $result->file->content);
+        self::assertSame(2, $result->applied);
+        self::assertSame(0, $result->skipped);
+    }
 }
diff --git a/tests/Unit/Runner/SourceScopeTest.php b/tests/Unit/Runner/SourceScopeTest.php
index 3d74c0a..a77a81a 100644
--- a/tests/Unit/Runner/SourceScopeTest.php
+++ b/tests/Unit/Runner/SourceScopeTest.php
@@ -7,6 +7,7 @@
 use DocbookCS\Diff\FileChange;
 use DocbookCS\Fix\Fix;
 use DocbookCS\Runner\RunScope;
+use DocbookCS\Sniff\FileEmptyLastLineSniffer;
 use DocbookCS\Source\File;
 use DocbookCS\Source\Line;
 use DocbookCS\Violation\SourceRange;
@@ -23,6 +24,7 @@
     CoversClass(RunScope::class),
     //
     UsesClass(FileChange::class),
+    UsesClass(FileEmptyLastLineSniffer::class),
     UsesClass(SourceRange::class),
     UsesClass(Violation::class),
 ]
@@ -172,6 +174,22 @@ public function itAnchorsADeletionAtTheEndOfTheFile(): void
         self::assertTrue($scope->includes($this->violation($untilOffset, $untilOffset, 2)));
     }
 
+    #[Test]
+    public function itScopesAnUnterminatedFileEndingToItsLastLine(): void
+    {
+        $file = new File('file.xml', "<root>\n</root>");
+        $document = new \DOMDocument();
+        $document->loadXML($file->content);
+        $violation = new FileEmptyLastLineSniffer()->process($document, $file)[0];
+
+        self::assertTrue(
+            RunScope::fromFileAndFileChange($file, new FileChange($file->path, [2]))->includes($violation),
+        );
+        self::assertFalse(
+            RunScope::fromFileAndFileChange($file, new FileChange($file->path, [1]))->includes($violation),
+        );
+    }
+
     private function violation(int $beginOffset, int $untilOffset, int $line): Violation
     {
         return new Violation(
diff --git a/tests/Unit/Sniff/FileEmptyLastLineSnifferTest.php b/tests/Unit/Sniff/FileEmptyLastLineSnifferTest.php
new file mode 100644
index 0000000..092b93b
--- /dev/null
+++ b/tests/Unit/Sniff/FileEmptyLastLineSnifferTest.php
@@ -0,0 +1,112 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DocbookCS\Tests\Unit\Sniff;
+
+use DocbookCS\Fix\Fixer\FileEmptyLastLineFixer;
+use DocbookCS\Sniff\FileEmptyLastLineSniffer;
+use DocbookCS\Source\File;
+use DocbookCS\Violation\SourceRange;
+use DocbookCS\Violation\Violation;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\Attributes\UsesClass;
+use PHPUnit\Framework\TestCase;
+
+#[
+    CoversClass(FileEmptyLastLineSniffer::class),
+    //
+    UsesClass(File::class),
+    UsesClass(SourceRange::class),
+    UsesClass(Violation::class),
+]
+final class FileEmptyLastLineSnifferTest extends TestCase
+{
+    #[Test]
+    public function itProvidesItsCodeAndFixer(): void
+    {
+        self::assertSame('DocbookCS.FileEmptyLastLine', FileEmptyLastLineSniffer::getCode());
+        self::assertSame(FileEmptyLastLineFixer::class, FileEmptyLastLineSniffer::getFixerClassName());
+    }
+
+    #[Test]
+    public function itAllowsExactlyOneLfEmptyLastLine(): void
+    {
+        self::assertSame([], $this->process("<root/>\n"));
+    }
+
+    #[Test, DataProvider('missingEndings')]
+    public function itReportsAnUnterminatedLastLine(string $content, string $affectedContent): void
+    {
+        $violation = $this->process($content)[0];
+        $beginOffset = strlen($content) - strlen($affectedContent);
+
+        self::assertSame('DocbookCS.FileEmptyLastLine', $violation->sniffCode);
+        self::assertSame('File must end with exactly one empty (LF) line.', $violation->message);
+        self::assertSame($affectedContent, $violation->rangeOne()->content);
+        self::assertSame($beginOffset, $violation->rangeOne()->beginOffset);
+        self::assertSame(strlen($content), $violation->rangeOne()->untilOffset);
+        self::assertSame(2, $violation->rangeOne()->line);
+    }
+
+    #[Test]
+    public function itReportsTheOnlyLineWhenItsEndingIsMissing(): void
+    {
+        $content = '<root/>';
+        $violation = $this->process($content)[0];
+
+        self::assertSame($content, $violation->rangeOne()->content);
+        self::assertSame(0, $violation->rangeOne()->beginOffset);
+        self::assertSame(strlen($content), $violation->rangeOne()->untilOffset);
+        self::assertSame(1, $violation->rangeOne()->line);
+    }
+
+    #[Test, DataProvider('nonCanonicalEndings')]
+    public function itReportsTheEntireNonCanonicalEnding(
+        string $content,
+        string $affectedContent,
+        int $expectedLine,
+    ): void {
+        $violation = $this->process($content)[0];
+        $beginOffset = strlen($content) - strlen($affectedContent);
+
+        self::assertSame($affectedContent, $violation->rangeOne()->content);
+        self::assertSame($beginOffset, $violation->rangeOne()->beginOffset);
+        self::assertSame(strlen($content), $violation->rangeOne()->untilOffset);
+        self::assertSame($expectedLine, $violation->rangeOne()->line);
+    }
+
+    /** @return iterable<string, array{string, string}> */
+    public static function missingEndings(): iterable
+    {
+        yield 'line feed file' => ["<root>\n</root>", '</root>'];
+        yield 'carriage return and line feed file' => ["<root>\r\n</root>", '</root>'];
+        yield 'carriage return file' => ["<root>\r</root>", '</root>'];
+        yield 'line feed at byte zero' => ["\n<root/>", '<root/>'];
+        yield 'carriage return and line feed at byte zero' => ["\r\n<root/>", '<root/>'];
+        yield 'carriage return at byte zero' => ["\r<root/>", '<root/>'];
+    }
+
+    /** @return iterable<string, array{string, string, int}> */
+    public static function nonCanonicalEndings(): iterable
+    {
+        yield 'carriage return and line feed' => ["<root/>\r\n", "\r\n", 1];
+        yield 'carriage return' => ["<root/>\r", "\r", 1];
+        yield 'line feeds' => ["<root/>\n\n", "\n\n", 1];
+        yield 'carriage returns and line feeds' => ["<root/>\r\n\r\n", "\r\n\r\n", 1];
+        yield 'carriage returns' => ["<root/>\r\r", "\r\r", 1];
+        yield 'multiple mixed endings' => ["<root/>\r\n\n\r", "\r\n\n\r", 1];
+        yield 'multiline file' => ["<root>\n</root>\r\n", "\r\n", 2];
+    }
+
+    /** @return list<Violation> */
+    private function process(string $content): array
+    {
+        $document = new \DOMDocument();
+        $document->loadXML($content);
+
+        return new FileEmptyLastLineSniffer()->process($document, new File('file.xml', $content));
+    }
+}