diff --git a/public_html/wp-content/mu-plugins/latest-site-hints.php b/public_html/wp-content/mu-plugins/latest-site-hints.php
index bca31578d9..f60988facd 100644
--- a/public_html/wp-content/mu-plugins/latest-site-hints.php
+++ b/public_html/wp-content/mu-plugins/latest-site-hints.php
@@ -7,6 +7,7 @@
 defined( 'WPINC' ) || die();
 
 add_action( 'wp', __NAMESPACE__ . '\maybe_add_latest_site_hints' );
+add_filter( 'jetpack_contact_form_html', __NAMESPACE__ . '\maybe_disable_contact_form' );
 
 /**
  * If user or bot visits WordCamp site that has newer site for the same city,
@@ -135,6 +136,86 @@ function show_notification_about_latest_site() {
 	'</p></div>';
 }
 
+/**
+ * Check if contact forms should be disabled on this site.
+ *
+ * Forms are disabled when:
+ * 1. There's a newer event site for this city, OR
+ * 2. The event ended more than 18 months ago.
+ *
+ * This reduces spam sent to organizers of past events.
+ *
+ * See https://github.com/WordPress/wordcamp.org/issues/1468
+ *
+ * @param string $html The contact form HTML.
+ *
+ * @return string The original form HTML or a replacement message.
+ */
+function maybe_disable_contact_form( $html ) {
+	global $current_blog;
+
+	$wordcamp = get_wordcamp_post();
+	$end_date = absint( $wordcamp->meta['End Date (YYYY-mm-dd)'][0] ?? 0 );
+
+	// Check if the event is still ongoing.
+	if ( $end_date && time() < ( (int) $end_date + DAY_IN_SECONDS ) ) {
+		return $html;
+	}
+
+	$has_newer_site  = false;
+	$expired_by_time = false;
+
+	// Check if the event ended more than 18 months ago.
+	if ( $end_date && time() > ( (int) $end_date + 18 * MONTH_IN_SECONDS ) ) {
+		$expired_by_time = true;
+	}
+
+	// Optimization: skip the newer-site database query during the first 3 months,
+	// since a new edition is unlikely to exist that soon.
+	if ( ! $expired_by_time && $end_date && time() < ( (int) $end_date + 3 * MONTH_IN_SECONDS ) ) {
+		return $html;
+	}
+
+	// Check if there's a newer site for this city.
+	$latest_domain = get_latest_home_url( $current_blog->domain, $current_blog->path );
+	if ( $latest_domain && trailingslashit( get_site_url() ) !== $latest_domain ) {
+		$has_newer_site = true;
+	}
+
+	if ( ! $has_newer_site && ! $expired_by_time ) {
+		return $html;
+	}
+
+	$event_name = esc_html( get_blog_details( $current_blog->blog_id )->blogname );
+
+	if ( $has_newer_site ) {
+		$message = wp_kses_post( sprintf(
+			// translators: %1$s is the event name, %2$s is the URL of the latest edition.
+			__( '<strong>%1$s</strong> is over. Please visit <a href="%2$s">the next edition</a> for more details and to get in touch.', 'wordcamporg' ),
+			$event_name,
+			esc_url( $latest_domain )
+		) );
+	} else {
+		$message = wp_kses_post( sprintf(
+			// translators: %s is the event name.
+			__( '<strong>%s</strong> is over and this contact form is no longer active.', 'wordcamporg' ),
+			$event_name
+		) );
+	}
+
+	$coc_message = wp_kses_post( sprintf(
+		// translators: %s is the mailto link for incident reports.
+		__( 'If you have a <a href="https://make.wordpress.org/handbook/community-code-of-conduct">Code of Conduct</a> concern, you can report it to the <a href="mailto:%s">WordPress Incident Response Team</a>.', 'wordcamporg' ),
+		'reports@wordpress.org'
+	) );
+
+	return sprintf(
+		'<div class="wordcamp-contact-form-disabled"><p>%s</p><p>%s</p></div>',
+		$message,
+		$coc_message
+	);
+}
+
 /**
  * Get the home URL of the most recent event in a given city.
  *
diff --git a/public_html/wp-content/mu-plugins/tests/test-disable-contact-form.php b/public_html/wp-content/mu-plugins/tests/test-disable-contact-form.php
new file mode 100644
index 0000000000..6075fb8961
--- /dev/null
+++ b/public_html/wp-content/mu-plugins/tests/test-disable-contact-form.php
@@ -0,0 +1,245 @@
+<?php
+
+namespace WordCamp\Latest_Site_Hints\Tests;
+use WP_UnitTest_Factory;
+use WordCamp\Tests\Database_TestCase;
+
+use function WordCamp\Latest_Site_Hints\maybe_disable_contact_form;
+
+defined( 'WPINC' ) || die();
+
+/**
+ * @group mu-plugins
+ * @group latest-site-hints
+ * @group disable-contact-form
+ */
+class Test_Disable_Contact_Form extends Database_TestCase {
+	/**
+	 * WordCamp post IDs created during setup, keyed by site ID.
+	 *
+	 * @var array
+	 */
+	protected static $wordcamp_post_ids = array();
+
+	/**
+	 * Sample contact form HTML used for testing.
+	 *
+	 * @var string
+	 */
+	protected static $sample_form_html = '<form><input type="text" name="name" /><input type="submit" /></form>';
+
+	/**
+	 * Create WordCamp posts on the central site for our test sites.
+	 *
+	 * @param WP_UnitTest_Factory $factory
+	 */
+	public static function wpSetUpBeforeClass( $factory ) {
+		parent::wpSetUpBeforeClass( $factory );
+
+		switch_to_blog( WORDCAMP_ROOT_BLOG_ID );
+
+		// Register the `wordcamp` post type if not already registered.
+		if ( ! post_type_exists( 'wordcamp' ) ) {
+			register_post_type( 'wordcamp' );
+		}
+
+		// Past event (2018 Seattle) - has a newer site (2019), ended long ago.
+		$past_event_id = wp_insert_post( array(
+			'post_type'   => 'wordcamp',
+			'post_title'  => 'WordCamp Seattle 2018',
+			'post_status' => 'publish',
+		) );
+		update_post_meta( $past_event_id, '_site_id', self::$year_dot_2018_site_id );
+		update_post_meta( $past_event_id, 'End Date (YYYY-mm-dd)', strtotime( '2018-06-15' ) );
+		self::$wordcamp_post_ids[ self::$year_dot_2018_site_id ] = $past_event_id;
+
+		// Current/future event (2019 Seattle) - newest site, end date in the future.
+		$current_event_id = wp_insert_post( array(
+			'post_type'   => 'wordcamp',
+			'post_title'  => 'WordCamp Seattle 2019',
+			'post_status' => 'publish',
+		) );
+		update_post_meta( $current_event_id, '_site_id', self::$year_dot_2019_site_id );
+		update_post_meta( $current_event_id, 'End Date (YYYY-mm-dd)', time() + YEAR_IN_SECONDS );
+		self::$wordcamp_post_ids[ self::$year_dot_2019_site_id ] = $current_event_id;
+
+		// Recent past event (Vancouver 2020) - newest site for city, ended 6 months ago.
+		$recent_past_id = wp_insert_post( array(
+			'post_type'   => 'wordcamp',
+			'post_title'  => 'WordCamp Vancouver 2020',
+			'post_status' => 'publish',
+		) );
+		update_post_meta( $recent_past_id, '_site_id', self::$slash_year_2020_site_id );
+		update_post_meta( $recent_past_id, 'End Date (YYYY-mm-dd)', time() - ( 6 * MONTH_IN_SECONDS ) );
+		self::$wordcamp_post_ids[ self::$slash_year_2020_site_id ] = $recent_past_id;
+
+		// Old event with no newer site (Vancouver 2016) - ended more than 18 months ago.
+		$old_event_id = wp_insert_post( array(
+			'post_type'   => 'wordcamp',
+			'post_title'  => 'WordCamp Vancouver 2016',
+			'post_status' => 'publish',
+		) );
+		update_post_meta( $old_event_id, '_site_id', self::$slash_year_2016_site_id );
+		update_post_meta( $old_event_id, 'End Date (YYYY-mm-dd)', strtotime( '2016-06-15' ) );
+		self::$wordcamp_post_ids[ self::$slash_year_2016_site_id ] = $old_event_id;
+
+		// Event with no end date (Japan yearless site).
+		$no_date_id = wp_insert_post( array(
+			'post_type'   => 'wordcamp',
+			'post_title'  => 'WordCamp Japan',
+			'post_status' => 'publish',
+		) );
+		update_post_meta( $no_date_id, '_site_id', self::$yearless_site_id );
+		self::$wordcamp_post_ids[ self::$yearless_site_id ] = $no_date_id;
+
+		restore_current_blog();
+	}
+
+	/**
+	 * Clean up WordCamp posts created during setup.
+	 */
+	public static function wpTearDownAfterClass() {
+		switch_to_blog( WORDCAMP_ROOT_BLOG_ID );
+
+		foreach ( self::$wordcamp_post_ids as $post_id ) {
+			wp_delete_post( $post_id, true );
+		}
+
+		restore_current_blog();
+
+		parent::wpTearDownAfterClass();
+	}
+
+	/**
+	 * Switch to the given blog and update the $current_blog global.
+	 *
+	 * `switch_to_blog()` does not update `$current_blog`, but
+	 * `maybe_disable_contact_form()` reads from it directly.
+	 *
+	 * @param int $blog_id The blog ID to switch to.
+	 */
+	protected function switch_to_blog_with_globals( $blog_id ) {
+		global $current_blog;
+
+		switch_to_blog( $blog_id );
+
+		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- Intentional for test setup.
+		$current_blog = get_site( $blog_id );
+	}
+
+	/**
+	 * Restore the previous blog and its $current_blog global.
+	 */
+	protected function restore_blog_with_globals() {
+		global $current_blog;
+
+		restore_current_blog();
+
+		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- Intentional for test teardown.
+		$current_blog = get_site( get_current_blog_id() );
+	}
+
+	/**
+	 * Test that contact forms are disabled when the event has a newer site.
+	 *
+	 * @covers WordCamp\Latest_Site_Hints\maybe_disable_contact_form
+	 */
+	public function test_past_event_with_newer_site_disables_form() {
+		$this->switch_to_blog_with_globals( self::$year_dot_2018_site_id );
+
+		$result = maybe_disable_contact_form( self::$sample_form_html );
+
+		$this->assertStringContainsString( 'wordcamp-contact-form-disabled', $result );
+		$this->assertStringContainsString( 'is over', $result );
+		$this->assertStringContainsString( 'the next edition', $result );
+		$this->assertStringNotContainsString( '<form', $result );
+
+		$this->restore_blog_with_globals();
+	}
+
+	/**
+	 * Test that contact forms are not disabled for current/future events.
+	 *
+	 * @covers WordCamp\Latest_Site_Hints\maybe_disable_contact_form
+	 */
+	public function test_current_event_keeps_form() {
+		$this->switch_to_blog_with_globals( self::$year_dot_2019_site_id );
+
+		$result = maybe_disable_contact_form( self::$sample_form_html );
+
+		$this->assertSame( self::$sample_form_html, $result );
+
+		$this->restore_blog_with_globals();
+	}
+
+	/**
+	 * Test that contact forms remain active for recent past events without a newer site.
+	 *
+	 * The Vancouver 2020 site is the newest for that city and ended only 6 months ago,
+	 * so neither the newer-site nor the 18-month expiry condition is met.
+	 *
+	 * @covers WordCamp\Latest_Site_Hints\maybe_disable_contact_form
+	 */
+	public function test_recent_past_event_without_newer_site_keeps_form() {
+		$this->switch_to_blog_with_globals( self::$slash_year_2020_site_id );
+
+		$result = maybe_disable_contact_form( self::$sample_form_html );
+
+		$this->assertSame( self::$sample_form_html, $result );
+
+		$this->restore_blog_with_globals();
+	}
+
+	/**
+	 * Test that contact forms are disabled when event ended more than 18 months ago.
+	 *
+	 * Vancouver 2016 has newer sites (2018-developers, 2020), so it will be disabled
+	 * via the newer-site path regardless, but the 18-month expiry also applies.
+	 *
+	 * @covers WordCamp\Latest_Site_Hints\maybe_disable_contact_form
+	 */
+	public function test_old_past_event_disables_form() {
+		$this->switch_to_blog_with_globals( self::$slash_year_2016_site_id );
+
+		$result = maybe_disable_contact_form( self::$sample_form_html );
+
+		$this->assertStringContainsString( 'wordcamp-contact-form-disabled', $result );
+		$this->assertStringNotContainsString( '<form', $result );
+
+		$this->restore_blog_with_globals();
+	}
+
+	/**
+	 * Test that the disabled message includes a Code of Conduct reporting link.
+	 *
+	 * @covers WordCamp\Latest_Site_Hints\maybe_disable_contact_form
+	 */
+	public function test_disabled_form_includes_coc_message() {
+		$this->switch_to_blog_with_globals( self::$year_dot_2018_site_id );
+
+		$result = maybe_disable_contact_form( self::$sample_form_html );
+
+		$this->assertStringContainsString( 'Code of Conduct', $result );
+		$this->assertStringContainsString( 'reports@wordpress.org', $result );
+
+		$this->restore_blog_with_globals();
+	}
+
+	/**
+	 * Test that contact forms are not modified when there is no end date set.
+	 *
+	 * When the end date is missing, the event is not treated as expired, and
+	 * the Japan yearless site has no newer site via domain pattern matching.
+	 *
+	 * @covers WordCamp\Latest_Site_Hints\maybe_disable_contact_form
+	 */
+	public function test_no_end_date_keeps_form() {
+		$this->switch_to_blog_with_globals( self::$yearless_site_id );
+
+		$result = maybe_disable_contact_form( self::$sample_form_html );
+
+		$this->assertSame( self::$sample_form_html, $result );
+
+		$this->restore_blog_with_globals();
+	}
+}