diff --git a/src/wp-includes/class-wp-query.php b/src/wp-includes/class-wp-query.php
index cf07b07d977c3..96fae867a3c6c 100644
--- a/src/wp-includes/class-wp-query.php
+++ b/src/wp-includes/class-wp-query.php
@@ -1431,7 +1431,36 @@ protected function parse_search( &$query_vars ) {
 			$query_vars['s'] = urldecode( $query_vars['s'] );
 		}
 		// There are no line breaks in <input /> fields.
-		$query_vars['s']                  = str_replace( array( "\r", "\n" ), '', $query_vars['s'] );
+		$query_vars['s'] = str_replace( array( "\r", "\n" ), '', $query_vars['s'] );
+		/*
+		 * Normalize Unicode whitespace (Zs category) to a regular half-width space
+		 * so that CJK ideographic spaces and other Unicode space separators are
+		 * recognized as word separators in the search query.
+		 *
+		 * @see https://core.trac.wordpress.org/ticket/44296
+		 */
+		$query_vars['s']                  = str_replace(
+			array(
+				"\u{00A0}", // No-Break Space.
+				"\u{1680}", // Ogham Space Mark.
+				"\u{2000}", // En Quad.
+				"\u{2001}", // Em Quad.
+				"\u{2002}", // En Space.
+				"\u{2003}", // Em Space.
+				"\u{2004}", // Three-Per-Em Space.
+				"\u{2005}", // Four-Per-Em Space.
+				"\u{2006}", // Six-Per-Em Space.
+				"\u{2007}", // Figure Space.
+				"\u{2008}", // Punctuation Space.
+				"\u{2009}", // Thin Space.
+				"\u{200A}", // Hair Space.
+				"\u{202F}", // Narrow No-Break Space.
+				"\u{205F}", // Medium Mathematical Space.
+				"\u{3000}", // Ideographic Space (CJK).
+			),
+			' ',
+			$query_vars['s']
+		);
 		$query_vars['search_terms_count'] = 1;
 		if ( ! empty( $query_vars['sentence'] ) ) {
 			$query_vars['search_terms'] = array( $query_vars['s'] );
diff --git a/tests/phpunit/tests/query/search.php b/tests/phpunit/tests/query/search.php
index 7bfbdec31c87d..bcab14fdf88ca 100644
--- a/tests/phpunit/tests/query/search.php
+++ b/tests/phpunit/tests/query/search.php
@@ -73,6 +73,39 @@ public function filter_wp_search_stopwords() {
 		return array();
 	}
 
+	/**
+	 * Tests that ideographic spaces are treated as separators even when stopwords are disabled.
+	 *
+	 * @ticket 44296
+	 */
+	public function test_ideographic_space_separator_with_no_stopwords() {
+		$terms = "This\u{3000}is\u{3000}a\u{3000}search\u{3000}term";
+		add_filter( 'wp_search_stopwords', array( $this, 'filter_wp_search_stopwords' ) );
+		$query = new WP_Query( array( 's' => $terms ) );
+		remove_filter( 'wp_search_stopwords', array( $this, 'filter_wp_search_stopwords' ) );
+
+		$this->assertSame( 5, $query->get( 'search_terms_count' ) );
+		$this->assertSame( array( 'This', 'is', 'search', 'term' ), $query->get( 'search_terms' ) );
+	}
+
+	/**
+	 * Tests that other Unicode space separators (Zs category) are also normalized.
+	 *
+	 * @ticket 44296
+	 */
+	public function test_unicode_space_separators_are_treated_as_separators() {
+		add_filter( 'wp_search_stopwords', array( $this, 'filter_wp_search_stopwords' ) );
+
+		// U+2003 Em Space — a representative Unicode Zs-category space.
+		$terms = "search\u{2003}term";
+		$query = new WP_Query( array( 's' => $terms ) );
+
+		remove_filter( 'wp_search_stopwords', array( $this, 'filter_wp_search_stopwords' ) );
+
+		$this->assertSame( 2, $query->get( 'search_terms_count' ) );
+		$this->assertSame( array( 'search', 'term' ), $query->get( 'search_terms' ) );
+	}
+
 	/**
 	 * @ticket 38099
 	 */