diff --git a/BigBite/Docs/Classes/StringableStandard.xml b/BigBite/Docs/Classes/StringableStandard.xml
new file mode 100644
index 0000000..dc46959
--- /dev/null
+++ b/BigBite/Docs/Classes/StringableStandard.xml
@@ -0,0 +1,27 @@
+<documentation title="Stringable">
+  <standard>
+  <![CDATA[
+  Classes that implement the "__toString" magic method should implement the Stringable interface.
+  ]]>
+  </standard>
+  <code_comparison>
+    <code title="Valid: Class implementing __toString implements the Stringable interface.">
+    <![CDATA[
+class Foo<em> implements Stringable</em> {
+  public function __toString(): string {
+    return __CLASS__;
+  }
+}
+    ]]>
+    </code>
+    <code title="Invalid: Class implementing __toString doesn't implement the Stringable interface.">
+    <![CDATA[
+class Foo<em></em> {
+  public function __toString(): string {
+    return __CLASS__;
+  }
+}
+    ]]>
+    </code>
+  </code_comparison>
+</documentation>
diff --git a/BigBite/Sniffs/Classes/StringableSniff.php b/BigBite/Sniffs/Classes/StringableSniff.php
new file mode 100644
index 0000000..8888732
--- /dev/null
+++ b/BigBite/Sniffs/Classes/StringableSniff.php
@@ -0,0 +1,107 @@
+<?php
+/**
+ * BigBite Coding Standards.
+ *
+ * @package BigBiteCS\BigBite
+ * @link    https://github.com/bigbite/phpcs-config
+ * @license https://opensource.org/licenses/MIT MIT
+ */
+
+namespace BigBiteCS\BigBite\Sniffs\Classes;
+
+use PHP_CodeSniffer\Files\File;
+use PHP_CodeSniffer\Sniffs\Sniff;
+use PHPCSUtils\Utils\ObjectDeclarations;
+
+/**
+ * Ensures classes that define a __toString method also implement the Stringable interface
+ */
+final class StringableSniff implements Sniff {
+
+	/**
+	 * A list of tokenizers this sniff supports.
+	 *
+	 * @var array<int,string>
+	 */
+	public $supportedTokenizers = array(
+		'PHP',
+	);
+
+	/**
+	 * Returns an array of tokens this test wants to listen for.
+	 *
+	 * @return array<int,int>
+	 */
+	public function register() {
+		if ( version_compare( phpversion(), '8.0.0', '<' ) ) {
+			return array();
+		}
+
+		return array( \T_FUNCTION );
+	}
+
+	/**
+	 * Processes this test, when one of its tokens is encountered.
+	 *
+	 * @param \PHP_CodeSniffer\Files\File $phpcsFile The file being scanned.
+	 * @param int                         $stackPtr  The position of the current token
+	 *                                               in the stack passed in $tokens.
+	 *
+	 * @return void
+	 */
+	public function process( File $phpcsFile, $stackPtr ) {
+		$tokens = $phpcsFile->getTokens();
+		$fnName = $phpcsFile->findNext( T_STRING, $stackPtr, ( $stackPtr + 5 ), false, null, true );
+
+		if ( false === $fnName || '__toString' !== $tokens[ $fnName ]['content'] ) {
+			return;
+		}
+
+		$classDecl = $phpcsFile->findPrevious( T_CLASS, $stackPtr, 0 );
+
+		// this __toString function isn't a class member?
+		if ( false === $classDecl ) {
+			return;
+		}
+
+		$interfaces = ObjectDeclarations::findImplementedInterfaceNames( $phpcsFile, $classDecl );
+
+		// we're good - class containing __toString implements the interface.
+		if ( is_array( $interfaces ) && in_array( 'Stringable', $interfaces, true ) ) {
+			return;
+		}
+
+		$message = 'Classes that declare "__toString" should implement the Stringable interface.';
+		$doWeFix = $phpcsFile->addFixableError( $message, $classDecl, 'NotImplemented', array(), 0 );
+
+		if ( true !== $doWeFix ) {
+			return;
+		}
+
+		$openingCurly = $tokens[ $classDecl ]['scope_opener'];
+
+		if ( $tokens[ $openingCurly ]['line'] === $tokens[ $classDecl ]['line'] ) {
+			$prevToken = $phpcsFile->findPrevious( T_STRING, $openingCurly, $classDecl );
+
+			if ( false === $prevToken ) {
+				return;
+			}
+
+			$phpcsFile->fixer->beginChangeset();
+			$phpcsFile->fixer->addContent( $prevToken, ' implements Stringable' );
+			$phpcsFile->fixer->endChangeset();
+
+			return;
+		}
+
+		$endOfLine = $phpcsFile->findPrevious( T_WHITESPACE, $openingCurly, $classDecl );
+
+		if ( false === $endOfLine ) {
+			return;
+		}
+
+		$phpcsFile->fixer->beginChangeset();
+		$phpcsFile->fixer->addContentBefore( $endOfLine, ' implements Stringable' );
+		$phpcsFile->fixer->endChangeset();
+	}
+}
diff --git a/BigBite/Tests/Classes/StringableUnitTest.1.inc b/BigBite/Tests/Classes/StringableUnitTest.1.inc
new file mode 100644
index 0000000..b15eae2
--- /dev/null
+++ b/BigBite/Tests/Classes/StringableUnitTest.1.inc
@@ -0,0 +1,29 @@
+<?php
+
+class DoesNotImplementToStringMagicMethod {
+}
+
+class CorrectlyImplementsStringable implements Stringable {
+  public function __toString(): string {
+    return __CLASS__;
+  }
+}
+
+class IncorrectWithWhitespace {
+  public function __toString(): string {
+    return __CLASS__;
+  }
+}
+
+class IncorrectWithNoWhitespace{
+  public function __toString(): string {
+    return __CLASS__;
+  }
+}
+
+class IncorrectWithNewline
+{
+  public function __toString(): string {
+    return __CLASS__;
+  }
+}
diff --git a/BigBite/Tests/Classes/StringableUnitTest.1.inc.fixed b/BigBite/Tests/Classes/StringableUnitTest.1.inc.fixed
new file mode 100644
index 0000000..af41b90
--- /dev/null
+++ b/BigBite/Tests/Classes/StringableUnitTest.1.inc.fixed
@@ -0,0 +1,29 @@
+<?php
+
+class DoesNotImplementToStringMagicMethod {
+}
+
+class CorrectlyImplementsStringable implements Stringable {
+  public function __toString(): string {
+    return __CLASS__;
+  }
+}
+
+class IncorrectWithWhitespace implements Stringable {
+  public function __toString(): string {
+    return __CLASS__;
+  }
+}
+
+class IncorrectWithNoWhitespace implements Stringable{
+  public function __toString(): string {
+    return __CLASS__;
+  }
+}
+
+class IncorrectWithNewline implements Stringable
+{
+  public function __toString(): string {
+    return __CLASS__;
+  }
+}
diff --git a/BigBite/Tests/Classes/StringableUnitTest.php b/BigBite/Tests/Classes/StringableUnitTest.php
new file mode 100644
index 0000000..357ac63
--- /dev/null
+++ b/BigBite/Tests/Classes/StringableUnitTest.php
@@ -0,0 +1,61 @@
+<?php
+/**
+ * Unit test class for BigBite Coding Standard.
+ *
+ * @package BigBiteCS\BigBite
+ * @link    https://github.com/bigbite/phpcs-config
+ * @license https://opensource.org/licenses/MIT MIT
+ */
+
+namespace BigBiteCS\BigBite\Tests\Classes;
+
+use BigBiteCS\BigBite\Tests\AbstractSniffUnitTest;
+
+/**
+ * Unit test class for the Stringable sniff.
+ *
+ * @package BigBiteCS\BigBite
+ */
+final class StringableUnitTest extends AbstractSniffUnitTest {
+
+	/**
+	 * Returns the lines where errors should occur.
+	 *
+	 * The key of the array should represent the line number and the value
+	 * should represent the number of errors that should occur on that line.
+	 *
+	 * @param string $testFile The name of the file being tested.
+	 *
+	 * @return array<int,int>
+	 */
+	public function getErrorList( $testFile = '' ) {
+		if ( version_compare( phpversion(), '8.0.0', '<' ) ) {
+			return array();
+		}
+
+		switch ( $testFile ) {
+			case 'StringableUnitTest.1.inc':
+				return array(
+					12 => 1,
+					18 => 1,
+					24 => 1,
+				);
+			default:
+				return array();
+		}
+	}
+
+	/**
+	 * Returns the lines where warnings should occur.
+	 *
+	 * The key of the array should represent the line number and the value
+	 * should represent the number of warnings that should occur on that line.
+	 *
+	 * @param string $testFile The name of the file being tested.
+	 *
+	 * @return array<int,int>
+	 */
+	public function getWarningList( $testFile = '' ) {
+		return array();
+	}
+}