diff --git a/src/wp-includes/formatting.php b/src/wp-includes/formatting.php
index e3681b071a2eb..a9288f65a98c4 100644
--- a/src/wp-includes/formatting.php
+++ b/src/wp-includes/formatting.php
@@ -227,8 +227,10 @@ function wptexturize( $text, $reset = false ) {
 	 */
 	$no_texturize_shortcodes = apply_filters( 'no_texturize_shortcodes', $default_no_texturize_shortcodes );
 
-	$no_texturize_tags_stack       = array();
-	$no_texturize_shortcodes_stack = array();
+	$no_texturize_tags_stack           = array();
+	$no_texturize_shortcodes_stack     = array();
+	$last_text_ends_with_quote_context = false;
+	$quote_after_inline_tag            = false;
 
 	// Look for shortcodes and HTML elements.
 
@@ -246,9 +248,11 @@ function wptexturize( $text, $reset = false ) {
 		if ( '<' === $first ) {
 			if ( str_starts_with( $curl, '<!--' ) ) {
 				// This is an HTML comment delimiter.
+				$quote_after_inline_tag = false;
 				continue;
 			} else {
 				// This is an HTML element delimiter.
+				$quote_after_inline_tag = $last_text_ends_with_quote_context && _wptexturize_is_inline_closing_tag( $curl );
 
 				// Replace each & with &#038; unless it already looks like an entity.
 				$curl = preg_replace( '/&(?!#(?:\d+|x[a-f0-9]+);|[a-z1-4]{1,8};)/i', '&#038;', $curl );
@@ -257,9 +261,11 @@ function wptexturize( $text, $reset = false ) {
 			}
 		} elseif ( '' === trim( $curl ) ) {
 			// This is a newline between delimiters. Performance improves when we check this.
+			$quote_after_inline_tag = false;
 			continue;
 
 		} elseif ( '[' === $first && $found_shortcodes && 1 === preg_match( '/^' . $shortcode_regex . '$/', $curl ) ) {
+			$quote_after_inline_tag = false;
 			// This is a shortcode delimiter.
 
 			if ( ! str_starts_with( $curl, '[[' ) && ! str_ends_with( $curl, ']]' ) ) {
@@ -274,6 +280,15 @@ function wptexturize( $text, $reset = false ) {
 
 			$curl = str_replace( $static_characters, $static_replacements, $curl );
 
+			if ( $quote_after_inline_tag ) {
+				if ( preg_match( "/^'[\p{L}\p{N}\p{Po}\p{Pf}\s.,;:!?\)\}\-&]|^'$/u", $curl ) ) {
+					$curl = $apos . substr( $curl, 1 );
+				} elseif ( preg_match( '/^"[\p{L}\p{N}\p{Po}\p{Pf}\s.,;:!?\)\}\-&]|^"$/u', $curl ) ) {
+					$curl = $closing_quote . substr( $curl, 1 );
+				}
+			}
+			$quote_after_inline_tag = false;
+
 			if ( str_contains( $curl, "'" ) ) {
 				$curl = preg_replace( $dynamic_characters['apos'], $dynamic_replacements['apos'], $curl );
 				$curl = wptexturize_primes( $curl, "'", $prime, $open_sq_flag, $closing_single_quote );
@@ -297,12 +312,96 @@ function wptexturize( $text, $reset = false ) {
 
 			// Replace each & with &#038; unless it already looks like an entity.
 			$curl = preg_replace( '/&(?!#(?:\d+|x[a-f0-9]+);|[a-z1-4]{1,8};)/i', '&#038;', $curl );
+
+			$last_text_ends_with_quote_context = _wptexturize_text_ends_with_quote_context( $curl );
+		} else {
+			$quote_after_inline_tag = false;
 		}
 	}
 
 	return implode( '', $textarr );
 }
 
+
+
+/**
+ * Determines whether text ends with a character that can provide quote context.
+ *
+ * This avoids running a Unicode regular expression for every text token in
+ * wptexturize(). Most tokens end with ASCII letters, numbers, or punctuation; only
+ * multibyte text and closing quote entities need a regular expression check.
+ *
+ * @since 7.0.0
+ *
+ * @param string $text Text token from wptexturize().
+ * @return bool Whether the text ends with quote context.
+ */
+function _wptexturize_text_ends_with_quote_context( $text ) {
+	if ( '' === $text ) {
+		return false;
+	}
+
+	$last_character = substr( $text, -1 );
+
+	if ( ctype_alnum( $last_character ) || in_array( $last_character, array( '.', '!', '?', ')' ), true ) ) {
+		return true;
+	}
+
+	if ( ';' === $last_character ) {
+		return (bool) preg_match( '/&#(?:8217|8221);$/', $text );
+	}
+
+	if ( ord( $last_character ) >= 0x80 ) {
+		return (bool) preg_match( '/[\p{L}\p{N}]$/u', $text );
+	}
+
+	return false;
+}
+
+/**
+ * Determines whether a token is a closing tag for a common inline HTML element.
+ *
+ * @since 7.0.0
+ *
+ * @param string $text A token from wptexturize()'s split input.
+ * @return bool Whether the token is a closing inline HTML element.
+ */
+function _wptexturize_is_inline_closing_tag( $text ) {
+	if ( ! preg_match( '/^<\/([a-z][a-z0-9]*)\s*>$/i', $text, $matches ) ) {
+		return false;
+	}
+
+	$inline_tags = array(
+		'a',
+		'abbr',
+		'b',
+		'bdi',
+		'bdo',
+		'cite',
+		'data',
+		'del',
+		'dfn',
+		'em',
+		'i',
+		'ins',
+		'label',
+		'mark',
+		'q',
+		's',
+		'samp',
+		'small',
+		'span',
+		'strong',
+		'sub',
+		'sup',
+		'time',
+		'u',
+		'var',
+	);
+
+	return in_array( strtolower( $matches[1] ), $inline_tags, true );
+}
+
 /**
  * Implements a logic tree to determine whether or not "7'." represents seven feet,
  * then converts the special char into either a prime char or a closing quote char.
diff --git a/tests/phpunit/tests/formatting/wpTexturize.php b/tests/phpunit/tests/formatting/wpTexturize.php
index fa81245c83bb9..56cb4271c2c60 100644
--- a/tests/phpunit/tests/formatting/wpTexturize.php
+++ b/tests/phpunit/tests/formatting/wpTexturize.php
@@ -157,6 +157,59 @@ public function test_other_html() {
 		// $this->assertSame( '&#8220;<strong>Quoted Text</strong>&#8221;,', wptexturize( '"<strong>Quoted Text</strong>",' ) );
 	}
 
+
+	/**
+	 * @ticket 18549
+	 */
+	public function test_historic_quotes_around_inline_html() {
+		$this->assertSame( 'The word is &#8220;<a href="http://example.com/">quoted</a>&#8221;.', wptexturize( 'The word is "<a href="http://example.com/">quoted</a>".' ) );
+		$this->assertSame( 'The word is &#8216;<a href="http://example.com/">quoted</a>&#8217;', wptexturize( 'The word is \'<a href="http://example.com/">quoted</a>\'' ) );
+		$this->assertSame( 'The word is &#8216;<a href="http://example.com/">quoted.</a>&#8217;', wptexturize( 'The word is \'<a href="http://example.com/">quoted.</a>\'' ) );
+		$this->assertSame( 'The word is &#8216;<a href="http://example.com/">quoted</a>&#8217;.', wptexturize( 'The word is \'<a href="http://example.com/">quoted</a>\'.' ) );
+		$this->assertSame( 'The word is &#8216;<a href="http://example.com/">quot</a>&#8217;d', wptexturize( 'The word is \'<a href="http://example.com/">quot</a>\'d' ) );
+	}
+
+	/**
+	 * @ticket 18549
+	 */
+	public function test_historic_texturize_around_html_cases() {
+		$this->assertSame( 'Here is &#8220;<a href="http://example.com">a test with a link</a>&#8221;', wptexturize( 'Here is "<a href="http://example.com">a test with a link</a>"' ) );
+		$this->assertSame( 'Here is &#8220;<a href="http://example.com">a test with a link and a period</a>&#8221;.', wptexturize( 'Here is "<a href="http://example.com">a test with a link and a period</a>".' ) );
+		$this->assertSame( 'Here is &#8220;<a href="http://example.com">a test with a link</a>&#8221;, and a comma.', wptexturize( 'Here is "<a href="http://example.com">a test with a link</a>", and a comma.' ) );
+		$this->assertSame( 'Here is &#8220;<a href="http://example.com">a test with a link</a>&#8221;; and a semi-colon.', wptexturize( 'Here is "<a href="http://example.com">a test with a link</a>"; and a semi-colon.' ) );
+		$this->assertSame( 'Here is &#8220;<a href="http://example.com">a test with a link</a>&#8221;- and a dash.', wptexturize( 'Here is "<a href="http://example.com">a test with a link</a>"- and a dash.' ) );
+		$this->assertSame( 'Here is &#8220;<a href="http://example.com">a test with a link</a>&#8221;&#8230; and ellipses.', wptexturize( 'Here is "<a href="http://example.com">a test with a link</a>"... and ellipses.' ) );
+		$this->assertSame( 'Here is &#8220;<a href="http://example.com">a test with a link</a>&#8221;… and a Unicode ellipsis.', wptexturize( 'Here is "<a href="http://example.com">a test with a link</a>"… and a Unicode ellipsis.' ) );
+		$this->assertSame( '&#8220;<em>引用</em>&#8221;。', wptexturize( '"<em>引用</em>"。' ) );
+		$this->assertSame( '&#8220;<em>引用</em>&#8221;，然后继续。', wptexturize( '"<em>引用</em>"，然后继续。' ) );
+		$this->assertSame( 'Here is &#8220;a test <a href="http://example.com">with a link</a>&#8221;.', wptexturize( 'Here is "a test <a href="http://example.com">with a link</a>".' ) );
+		$this->assertSame( 'Here is &#8220;<a href="http://example.com">a test with a link</a>&#8221;and a word stuck to the end.', wptexturize( 'Here is "<a href="http://example.com">a test with a link</a>"and a word stuck to the end.' ) );
+		$this->assertSame( '&#8216;<strong>Quoted Text</strong>&#8217;,', wptexturize( "'<strong>Quoted Text</strong>'," ) );
+		$this->assertSame( '&#8220;<strong>Quoted Text</strong>&#8221;,', wptexturize( '"<strong>Quoted Text</strong>",' ) );
+		$this->assertSame( '<strong>Read more: </strong>&#8220;<a>Something (else)</a>&#8221;</p>', wptexturize( '<strong>Read more: </strong>"<a>Something (else)</a>"</p>' ) );
+	}
+
+	/**
+	 * @ticket 18549
+	 */
+	public function test_historic_apostrophe_after_inline_formatting_tag() {
+		$this->assertSame( '<strong>He</strong>&#8217;s here.', wptexturize( "<strong>He</strong>'s here." ) );
+		$this->assertSame( '<em>It</em>&#8217;s fine.', wptexturize( "<em>It</em>'s fine." ) );
+		$this->assertSame( '<a href="http://example.org">Dan</a>&#8217;s truck', wptexturize( '<a href="http://example.org">Dan</a>\'s truck' ) );
+		$this->assertSame( '<strong>rock</strong>&#8217;n&#8217;roll', wptexturize( "<strong>rock</strong>'n'roll" ) );
+		$this->assertSame( '&#038;<strong>x</strong>&#8217;s', wptexturize( "&<strong>x</strong>'s" ) );
+		$this->assertSame( '<em>&#8220;John&#8221;</em>&#8217;s', wptexturize( '<em>"John"</em>\'s' ) );
+		$this->assertSame( '<em>&#8216;John&#8217;</em>&#8217;s', wptexturize( "<em>'John'</em>'s" ) );
+	}
+
+	/**
+	 * @ticket 18549
+	 */
+	public function test_historic_inline_tag_quote_requires_adjacency() {
+		$this->assertSame( '<strong>He</strong> &#8216;go&#8217;', wptexturize( "<strong>He</strong> 'go'" ) );
+		$this->assertSame( '<strong>He said</strong> &#8220;go&#8221;', wptexturize( '<strong>He said</strong> "go"' ) );
+	}
+
 	public function test_x() {
 		$this->assertSame( '14&#215;24', wptexturize( '14x24' ) );
 	}