diff --git a/WordPress-Extra/ruleset.xml b/WordPress-Extra/ruleset.xml
index ab0e8db3b7..a1d36cc955 100644
--- a/WordPress-Extra/ruleset.xml
+++ b/WordPress-Extra/ruleset.xml
@@ -187,6 +187,11 @@
 	<!-- Detect use of double negative `!!`. -->
 	<rule ref="Universal.CodeAnalysis.NoDoubleNegative"/>
 
+	<!-- Flags calls to get_*_meta() and get_metadata*() functions
+	     that include the $key/$meta_key parameter but omit the $single parameter.
+	     https://github.com/WordPress/WordPress-Coding-Standards/issues/2459 -->
+	<rule ref="WordPress.WP.GetMetaSingle"/>
+
 	<!--
 	#############################################################################
 	Code style sniffs for more recent PHP features and syntaxes.
diff --git a/WordPress/Docs/WP/GetMetaSingleStandard.xml b/WordPress/Docs/WP/GetMetaSingleStandard.xml
new file mode 100644
index 0000000000..dc27694007
--- /dev/null
+++ b/WordPress/Docs/WP/GetMetaSingleStandard.xml
@@ -0,0 +1,33 @@
+<?xml version="1.0"?>
+<documentation xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="https://phpcsstandards.github.io/PHPCSDevTools/phpcsdocs.xsd"
+    title="Get Meta Single"
+    >
+    <standard>
+    <![CDATA[
+When calling the get_(comment|post|site|term|user)_meta(), get_metadata(), get_metadata_default(),
+and get_metadata_raw() functions, if the $meta_key/$key parameter is passed, the $single parameter
+should be passed as well to make it explicit what is the expected return type.
+    ]]>
+    </standard>
+    <code_comparison>
+        <code title="Valid: get meta functions used with or without both $meta_key/$key and $single parameters.">
+        <![CDATA[
+$admin_color = get_user_meta(
+    $user_id,
+    <em>'admin_color',
+    true</em>
+);
+$post_meta = get_metadata( 'post', $post_id<em></em> );
+        ]]>
+        </code>
+        <code title="Invalid: get meta function used with $meta_key/$key parameter and without $single parameter.">
+        <![CDATA[
+$admin_color = get_user_meta(
+    $user_id,
+    <em>'admin_color'</em>
+);
+        ]]>
+        </code>
+    </code_comparison>
+</documentation>
diff --git a/WordPress/Sniffs/WP/GetMetaSingleSniff.php b/WordPress/Sniffs/WP/GetMetaSingleSniff.php
new file mode 100644
index 0000000000..562991679e
--- /dev/null
+++ b/WordPress/Sniffs/WP/GetMetaSingleSniff.php
@@ -0,0 +1,172 @@
+<?php
+/**
+ * WordPress Coding Standard.
+ *
+ * @package WPCS\WordPressCodingStandards
+ * @link    https://github.com/WordPress/WordPress-Coding-Standards
+ * @license https://opensource.org/licenses/MIT MIT
+ */
+
+namespace WordPressCS\WordPress\Sniffs\WP;
+
+use PHPCSUtils\Utils\PassedParameters;
+use WordPressCS\WordPress\AbstractFunctionParameterSniff;
+
+/**
+ * Flags calls to get_(comment|post|site|term|user)_meta(), get_metadata(), get_metadata_default()
+ * and get_metadata_raw() functions that include the $key/$meta_key parameter, but omit the $single
+ * parameter. Omitting $single in this situation can result in unexpected return types and lead to
+ * bugs.
+ *
+ * @link https://github.com/WordPress/WordPress-Coding-Standards/issues/2459
+ *
+ * @since 3.2.0
+ */
+final class GetMetaSingleSniff extends AbstractFunctionParameterSniff {
+
+	/**
+	 * The group name for this group of functions.
+	 *
+	 * @since 3.2.0
+	 *
+	 * @var string
+	 */
+	protected $group_name = 'get_meta';
+
+	/**
+	 * List of functions this sniff should examine.
+	 *
+	 * @link https://developer.wordpress.org/reference/functions/get_comment_meta/
+	 * @link https://developer.wordpress.org/reference/functions/get_metadata/
+	 * @link https://developer.wordpress.org/reference/functions/get_metadata_default/
+	 * @link https://developer.wordpress.org/reference/functions/get_metadata_raw/
+	 * @link https://developer.wordpress.org/reference/functions/get_post_meta/
+	 * @link https://developer.wordpress.org/reference/functions/get_site_meta/
+	 * @link https://developer.wordpress.org/reference/functions/get_term_meta/
+	 * @link https://developer.wordpress.org/reference/functions/get_user_meta/
+	 *
+	 * @since 3.2.0
+	 *
+	 * @var array<string, array> Key is function name, value is an array containing information
+	 *                           about the name and position of the relevant parameters.
+	 */
+	protected $target_functions = array(
+		'get_comment_meta'     => array(
+			'condition'   => array(
+				'parameter' => 'key',
+				'position'  => 2,
+			),
+			'recommended' => array(
+				'parameter' => 'single',
+				'position'  => 3,
+			),
+		),
+		'get_metadata'         => array(
+			'condition'   => array(
+				'parameter' => 'meta_key',
+				'position'  => 3,
+			),
+			'recommended' => array(
+				'parameter' => 'single',
+				'position'  => 4,
+			),
+		),
+		'get_metadata_default' => array(
+			'condition'   => array(
+				'parameter' => 'meta_key',
+				'position'  => 3,
+			),
+			'recommended' => array(
+				'parameter' => 'single',
+				'position'  => 4,
+			),
+		),
+		'get_metadata_raw'     => array(
+			'condition'   => array(
+				'parameter' => 'meta_key',
+				'position'  => 3,
+			),
+			'recommended' => array(
+				'parameter' => 'single',
+				'position'  => 4,
+			),
+		),
+		'get_post_meta'        => array(
+			'condition'   => array(
+				'parameter' => 'key',
+				'position'  => 2,
+			),
+			'recommended' => array(
+				'parameter' => 'single',
+				'position'  => 3,
+			),
+		),
+		'get_site_meta'        => array(
+			'condition'   => array(
+				'parameter' => 'key',
+				'position'  => 2,
+			),
+			'recommended' => array(
+				'parameter' => 'single',
+				'position'  => 3,
+			),
+		),
+		'get_term_meta'        => array(
+			'condition'   => array(
+				'parameter' => 'key',
+				'position'  => 2,
+			),
+			'recommended' => array(
+				'parameter' => 'single',
+				'position'  => 3,
+			),
+		),
+		'get_user_meta'        => array(
+			'condition'   => array(
+				'parameter' => 'key',
+				'position'  => 2,
+			),
+			'recommended' => array(
+				'parameter' => 'single',
+				'position'  => 3,
+			),
+		),
+	);
+
+	/**
+	 * Process the parameters of a matched function.
+	 *
+	 * @since 3.2.0
+	 *
+	 * @param int    $stackPtr        The position of the current token in the stack.
+	 * @param string $group_name      The name of the group which was matched.
+	 * @param string $matched_content The token content (function name) which was matched
+	 *                                in lowercase.
+	 * @param array  $parameters      Array with information about the parameters.
+	 *
+	 * @return void
+	 */
+	public function process_parameters( $stackPtr, $group_name, $matched_content, $parameters ) {
+		$condition   = $this->target_functions[ $matched_content ]['condition'];
+		$recommended = $this->target_functions[ $matched_content ]['recommended'];
+
+		$meta_key = PassedParameters::getParameterFromStack( $parameters, $condition['position'], $condition['parameter'] );
+		if ( false === $meta_key ) {
+			return;
+		}
+
+		$single = PassedParameters::getParameterFromStack( $parameters, $recommended['position'], $recommended['parameter'] );
+		if ( is_array( $single ) ) {
+			return;
+		}
+
+		$tokens = $this->phpcsFile->getTokens();
+
+		$this->phpcsFile->addWarning(
+			'When passing the $%s parameter to %s(), the $%s parameter must also be passed to make it explicit whether an array or a string is expected.',
+			$stackPtr,
+			'ReturnTypeNotExplicit',
+			array( $condition['parameter'], $tokens[ $stackPtr ]['content'], $recommended['parameter'] )
+		);
+	}
+}
diff --git a/WordPress/Tests/WP/GetMetaSingleUnitTest.inc b/WordPress/Tests/WP/GetMetaSingleUnitTest.inc
new file mode 100644
index 0000000000..80d47d4b02
--- /dev/null
+++ b/WordPress/Tests/WP/GetMetaSingleUnitTest.inc
@@ -0,0 +1,32 @@
+<?php
+
+// Invalid calls (missing mandatory parameter), but still useful to check that the sniff does not flag them.
+$invalid_but_ok = get_post_meta();
+$invalid_but_ok = get_post_meta( single: true, $post_id );
+$invalid_but_ok = get_post_meta( single: true );
+$invalid_but_ok = get_metadata( 'post' );
+
+$ok = get_post_meta( $post_id );
+$ok = get_post_meta( $post_id, $meta_key, false );
+$ok = get_post_meta( $post_id, single: true );
+$ok = get_post_meta( $post_id, single: true, key: $meta_key );
+$ok = get_metadata( 'post', $post_id );
+$ok = get_metadata( 'post', $post_id, $meta_key, true );
+$ok = get_metadata( 'post', $post_id, single: true );
+$ok = get_metadata( 'post', $post_id, single: true, meta_key: $meta_key );
+
+$warning = get_post_meta( $post_id, $meta_key );
+$warning = get_post_meta( $post_id, key: $meta_key );
+$warning = get_post_meta( $post_id, key: $meta_key, sinngle: true ); // Typo in parameter name.
+$warning = get_comment_meta( $comment_id, $meta_key );
+$warning = get_site_meta( $site_id, $meta_key );
+$warning = get_term_meta( $term_id, $meta_key );
+$warning = get_user_meta( $user_id, $meta_key );
+$warning = GET_METADATA( 'post', $post_id, $meta_key );
+$warning = get_metadata(
+    'post',
+    $post_id,
+    meta_key: $meta_key
+);
+$warning = get_metadata_raw( 'post', $post_id, $meta_key );
+$warning = get_metadata_default( 'post', $post_id, $meta_key );
diff --git a/WordPress/Tests/WP/GetMetaSingleUnitTest.php b/WordPress/Tests/WP/GetMetaSingleUnitTest.php
new file mode 100644
index 0000000000..20d909e8cf
--- /dev/null
+++ b/WordPress/Tests/WP/GetMetaSingleUnitTest.php
@@ -0,0 +1,52 @@
+<?php
+/**
+ * Unit test class for WordPress Coding Standard.
+ *
+ * @package WPCS\WordPressCodingStandards
+ * @link    https://github.com/WordPress/WordPress-Coding-Standards
+ * @license https://opensource.org/licenses/MIT MIT
+ */
+
+namespace WordPressCS\WordPress\Tests\WP;
+
+use PHP_CodeSniffer\Tests\Standards\AbstractSniffUnitTest;
+
+/**
+ * Unit test class for the GetMetaSingle sniff.
+ *
+ * @since 3.2.0
+ *
+ * @covers \WordPressCS\WordPress\Sniffs\WP\GetMetaSingleSniff
+ */
+final class GetMetaSingleUnitTest extends AbstractSniffUnitTest {
+
+	/**
+	 * Returns the lines where errors should occur.
+	 *
+	 * @return array<int, int> Key is the line number, value is the number of expected errors.
+	 */
+	public function getErrorList() {
+		return array();
+	}
+
+	/**
+	 * Returns the lines where warnings should occur.
+	 *
+	 * @return array<int, int> Key is the line number, value is the number of expected warnings.
+	 */
+	public function getWarningList() {
+		return array(
+			18 => 1,
+			19 => 1,
+			20 => 1,
+			21 => 1,
+			22 => 1,
+			23 => 1,
+			24 => 1,
+			25 => 1,
+			26 => 1,
+			31 => 1,
+			32 => 1,
+		);
+	}
+}