diff --git a/src/js/_enqueues/admin/common.js b/src/js/_enqueues/admin/common.js
index 2a7daba0d2dc4..c3d49310e8897 100644
--- a/src/js/_enqueues/admin/common.js
+++ b/src/js/_enqueues/admin/common.js
@@ -2356,3 +2356,242 @@ $( function( $ ) {
 	// Expose public methods.
 	return pub;
 })();
+
+/**
+ * Validate the delete-and-reassign users form and surface an accessible
+ * error summary instead of disabling the submit button.
+ *
+ * Disabled buttons can't be discovered by assistive technology, so rather
+ * than blocking submission we let the form submit, intercept it when content
+ * decisions are still missing, and present a focusable error summary that
+ * lists how many decisions remain and links straight to each one.
+ *
+ * Shared by both the single-site (wp-admin/users.php) and multisite/network
+ * (confirm_delete_users() in wp-admin/includes/ms.php) deletion forms. The two
+ * differ in markup: single site has one content decision per user, multisite
+ * has one decision per site a user belongs to (several radio groups per
+ * fieldset), and their reassign dropdowns use different "no selection" values.
+ * The logic below works per radio group so it covers both.
+ *
+ * @since 7.1.0
+ */
+(function(){
+	const { _n, sprintf } = wp.i18n;
+	const usersForm = document.querySelector( '.delete-and-reassign-users-form' );
+
+	// Check if the form exists and contains any radio buttons.
+	if ( ! usersForm || ! usersForm.querySelector( 'input[type="radio"]' ) ) {
+		return;
+	}
+
+	const summaryId = 'delete-users-error-summary';
+
+	/**
+	 * Whether a reassign dropdown has no user selected.
+	 *
+	 * The "Select a user" placeholder value differs between the forms: the
+	 * single-site dropdown uses an empty string, the multisite one uses the
+	 * wp_dropdown_users() default of '-1'.
+	 *
+	 * @param {HTMLSelectElement} select The reassign dropdown.
+	 * @return {boolean} True when no real user is selected.
+	 */
+	function hasNoSelectedUser( select ) {
+		return '' === select.value || '-1' === select.value;
+	}
+
+	/**
+	 * Builds a human-readable label for a radio group's decision.
+	 *
+	 * Combines the fieldset legend (the user) with the site context that
+	 * precedes the group on multisite, so each summary entry is identifiable.
+	 *
+	 * @param {HTMLElement} group The radio group (<ul>) element.
+	 * @return {string} The composed label.
+	 */
+	function getDecisionLabel( group ) {
+		const fieldset = group.closest( 'fieldset' );
+		const legend   = fieldset ? fieldset.querySelector( 'legend' ) : null;
+		const parts    = [];
+
+		if ( legend ) {
+			parts.push( legend.textContent.trim() );
+		}
+
+		// On multisite each radio group is preceded by a "Site: …" paragraph.
+		const previous = group.previousElementSibling;
+		if ( previous && previous !== legend && previous.textContent.trim() ) {
+			parts.push( previous.textContent.trim() );
+		}
+
+		return parts.join( ' – ' );
+	}
+
+	// Keep the radio selection in sync with the reassign dropdown.
+	usersForm.querySelectorAll( 'select' ).forEach( function( selectElement ) {
+		selectElement.addEventListener( 'change', function( e ) {
+			const item  = e.target.closest( 'li' );
+			const radio = item ? item.querySelector( 'input[type="radio"]' ) : null;
+			if ( radio ) {
+				radio.checked = ! hasNoSelectedUser( e.target );
+			}
+		});
+	});
+
+	/**
+	 * Returns the radio groups whose content decision is still incomplete.
+	 *
+	 * A decision unit is a single radio group (<ul>), which maps to one user on
+	 * single site and one site-per-user on multisite.
+	 *
+	 * @return {Array} Objects describing each incomplete decision.
+	 */
+	function getIncompleteDecisions() {
+		const incomplete = [];
+
+		usersForm.querySelectorAll( 'fieldset ul' ).forEach( function( group ) {
+			const radios = group.querySelectorAll( 'input[type="radio"]' );
+			if ( ! radios.length ) {
+				return;
+			}
+
+			const checked = group.querySelector( 'input[type="radio"]:checked' );
+
+			// No option chosen yet.
+			if ( ! checked ) {
+				incomplete.push( { target: radios[ 0 ], label: getDecisionLabel( group ) } );
+				return;
+			}
+
+			// "Attribute to another user" chosen, but no user selected.
+			if ( 'reassign' === checked.value ) {
+				const select = group.querySelector( 'select' );
+				if ( select && hasNoSelectedUser( select ) ) {
+					incomplete.push( { target: select, label: getDecisionLabel( group ) } );
+				}
+			}
+		});
+
+		return incomplete;
+	}
+
+	/**
+	 * Builds or refreshes the error summary markup.
+	 *
+	 * @param {Array} incomplete Incomplete decisions from getIncompleteDecisions().
+	 * @return {string} The summary title, for announcing to assistive technology.
+	 */
+	function renderErrorSummary( incomplete ) {
+		let summary = document.getElementById( summaryId );
+
+		if ( ! summary ) {
+			summary = document.createElement( 'div' );
+			summary.id = summaryId;
+			summary.className = 'notice notice-error';
+			summary.setAttribute( 'tabindex', '-1' );
+
+			// The wrapper contains the form on single site and wraps it on
+			// multisite; insert the summary right after the page heading.
+			const wrap    = usersForm.querySelector( '.wrap' ) || usersForm.closest( '.wrap' ) || usersForm;
+			const heading = wrap.querySelector( 'h1' );
+			wrap.insertBefore( summary, heading ? heading.nextSibling : wrap.firstChild );
+		}
+
+		const count = incomplete.length;
+		const title = sprintf(
+			/* translators: %s: Number of content decisions still required. */
+			_n(
+				'%s content decision is still required before you can delete.',
+				'%s content decisions are still required before you can delete.',
+				count
+			),
+			count
+		);
+
+		// Clear any previous markup and invalid states before rebuilding,
+		// so decisions resolved since the last render are no longer flagged.
+		summary.textContent = '';
+		usersForm.querySelectorAll( '[aria-invalid]' ).forEach( function( el ) {
+			el.removeAttribute( 'aria-invalid' );
+		});
+
+		const titleEl = document.createElement( 'p' );
+		const strong  = document.createElement( 'strong' );
+		strong.textContent = title;
+		titleEl.appendChild( strong );
+		summary.appendChild( titleEl );
+
+		const list = document.createElement( 'ul' );
+		incomplete.forEach( function( item ) {
+			const li   = document.createElement( 'li' );
+			const link = document.createElement( 'a' );
+			link.href        = '#' + item.target.id;
+			link.textContent = item.label;
+			link.addEventListener( 'click', function( e ) {
+				e.preventDefault();
+				item.target.focus();
+			});
+			li.appendChild( link );
+			list.appendChild( li );
+
+			item.target.setAttribute( 'aria-invalid', 'true' );
+		});
+		summary.appendChild( list );
+
+		return title;
+	}
+
+	/**
+	 * Removes the error summary and clears invalid states.
+	 */
+	function clearErrorState() {
+		const summary = document.getElementById( summaryId );
+		if ( summary ) {
+			summary.remove();
+		}
+		usersForm.querySelectorAll( '[aria-invalid]' ).forEach( function( el ) {
+			el.removeAttribute( 'aria-invalid' );
+		});
+	}
+
+	/**
+	 * Refreshes the error summary to match the current form state.
+	 *
+	 * @param {boolean} moveFocus Whether to move focus to the summary and
+	 *                            announce it (used on a failed submit).
+	 * @return {number} The number of incomplete decisions.
+	 */
+	function updateSummary( moveFocus ) {
+		const incomplete = getIncompleteDecisions();
+
+		if ( ! incomplete.length ) {
+			clearErrorState();
+			return 0;
+		}
+
+		const title = renderErrorSummary( incomplete );
+
+		if ( moveFocus ) {
+			document.getElementById( summaryId ).focus();
+			if ( window.wp && window.wp.a11y ) {
+				window.wp.a11y.speak( title, 'assertive' );
+			}
+		}
+
+		return incomplete.length;
+	}
+
+	usersForm.addEventListener( 'submit', function( e ) {
+		if ( updateSummary( true ) > 0 ) {
+			e.preventDefault();
+		}
+	});
+
+	// Keep an existing summary current as decisions are resolved, without
+	// stealing focus on every interaction.
+	usersForm.addEventListener( 'change', function() {
+		if ( document.getElementById( summaryId ) ) {
+			updateSummary( false );
+		}
+	});
+})();
diff --git a/src/wp-admin/css/common.css b/src/wp-admin/css/common.css
index 53933f0ac28a2..47ef4cf07dcae 100644
--- a/src/wp-admin/css/common.css
+++ b/src/wp-admin/css/common.css
@@ -2605,6 +2605,23 @@ body.iframe {
 	display: block;
 }
 
+.delete-and-reassign-users-form legend {
+	margin: 1em 0;
+	line-height: 1.5;
+	float: inline-start;
+}
+
+.delete-and-reassign-users-form fieldset > fieldset,
+.delete-and-reassign-users-form fieldset > ul {
+	clear: both;
+}
+
+.delete-and-reassign-users-form fieldset:has(select[aria-invalid="true"]):not(fieldset:has(fieldset)) {
+	border-left: 4px solid #cc1818;
+	background: #fcf0f0;
+	padding-left: 12px;
+}
+
 .importers {
 	font-size: 16px;
 	width: auto;
diff --git a/src/wp-admin/includes/deprecated.php b/src/wp-admin/includes/deprecated.php
index 86524fb897311..1dcf08a0a34c1 100644
--- a/src/wp-admin/includes/deprecated.php
+++ b/src/wp-admin/includes/deprecated.php
@@ -1589,3 +1589,14 @@ function image_attachment_fields_to_save( $post, $attachment ) {
 
 	return $post;
 }
+
+/**
+ * Was used to add JavaScript to the delete users form.
+ *
+ * @since 3.5.0
+ * @deprecated 7.1.0
+ * @access private
+ */
+function delete_users_add_js() {
+	_deprecated_function( __FUNCTION__, '7.1.0' );
+}
diff --git a/src/wp-admin/includes/ms.php b/src/wp-admin/includes/ms.php
index be87d05aead58..50066bf14d18c 100644
--- a/src/wp-admin/includes/ms.php
+++ b/src/wp-admin/includes/ms.php
@@ -856,12 +856,15 @@ function _thickbox_path_admin_subfolder() {
  * @return bool
  */
 function confirm_delete_users( $users ) {
+	global $wpdb;
+
 	$current_user = wp_get_current_user();
 	if ( ! is_array( $users ) || empty( $users ) ) {
 		return false;
 	}
+
 	?>
-	<h1><?php esc_html_e( 'Users' ); ?></h1>
+	<h1><?php esc_html_e( 'Delete Users' ); ?></h1>
 
 	<?php if ( 1 === count( $users ) ) : ?>
 		<p><?php _e( 'You have chosen to delete the user from all networks and sites.' ); ?></p>
@@ -869,17 +872,15 @@ function confirm_delete_users( $users ) {
 		<p><?php _e( 'You have chosen to delete the following users from all networks and sites.' ); ?></p>
 	<?php endif; ?>
 
-	<form action="users.php?action=dodelete" method="post">
+	<form action="users.php?action=dodelete" method="post" class="delete-and-reassign-users-form">
 	<input type="hidden" name="dodelete" />
 	<?php
 	wp_nonce_field( 'ms-users-delete' );
 	$site_admins = get_super_admins();
-	$admin_out   = '<option value="' . esc_attr( $current_user->ID ) . '">' . $current_user->user_login . '</option>';
 	?>
 	<table class="form-table" role="presentation">
 	<?php
-	$allusers = (array) $_POST['allusers'];
-	foreach ( $allusers as $user_id ) {
+	foreach ( $users as $user_id ) {
 		if ( '' !== $user_id && '0' !== $user_id ) {
 			$delete_user = get_userdata( $user_id );
 
@@ -902,6 +903,7 @@ function confirm_delete_users( $users ) {
 					)
 				);
 			}
+
 			?>
 			<tr>
 				<th scope="row"><?php echo $delete_user->user_login; ?>
@@ -912,60 +914,104 @@ function confirm_delete_users( $users ) {
 
 			if ( ! empty( $blogs ) ) {
 				?>
-				<td><fieldset><p><legend>
+				<td><fieldset><legend>
 				<?php
 				printf(
-					/* translators: %s: User login. */
-					__( 'What should be done with content owned by %s?' ),
-					'<em>' . $delete_user->user_login . '</em>'
+					/* translators: 1: User login, 2: User ID. */
+					__( '%1$s (ID #%2$s): What should be done with the content owned by this user?' ),
+					'<strong>' . $delete_user->user_login . '</strong>',
+					$user_id
 				);
 				?>
-				</legend></p>
+				</legend>
 				<?php
 				foreach ( (array) $blogs as $key => $details ) {
 					$blog_users = get_users(
 						array(
 							'blog_id' => $details->userblog_id,
-							'fields'  => array( 'ID', 'user_login' ),
+							'fields'  => array( 'ID' ),
+							'exclude' => $users,
 						)
 					);
 
+					$blog_users = wp_list_pluck( $blog_users, 'ID' );
+
 					if ( is_array( $blog_users ) && ! empty( $blog_users ) ) {
-						$user_site     = "<a href='" . esc_url( get_home_url( $details->userblog_id ) ) . "'>{$details->blogname}</a>";
-						$user_dropdown = '<label for="reassign_user" class="screen-reader-text">' .
-								/* translators: Hidden accessibility text. */
-								__( 'Select a user' ) .
-							'</label>';
-						$user_dropdown .= "<select name='blog[$user_id][$key]' id='reassign_user'>";
-						$user_list      = '';
-
-						foreach ( $blog_users as $user ) {
-							if ( ! in_array( (int) $user->ID, $allusers, true ) ) {
-								$user_list .= "<option value='{$user->ID}'>{$user->user_login}</option>";
+						$user_site = "<a href='" . esc_url( get_home_url( $details->userblog_id ) ) . "'>{$details->blogname}</a>";
+						switch_to_blog( $details->userblog_id );
+						/* This filter is documented in wp-admin/users.php */
+						$user_has_content = (bool) apply_filters( 'users_have_additional_content', false, array( $delete_user->ID ) );
+
+						if ( ! $user_has_content ) {
+							if ( $wpdb->get_var(
+								$wpdb->prepare(
+									"SELECT ID FROM {$wpdb->posts}
+									WHERE post_author = %d
+									LIMIT 1",
+									$delete_user->ID
+								)
+							) ) {
+								$user_has_content = true;
+							} elseif ( $wpdb->get_var(
+								$wpdb->prepare(
+									"SELECT link_id FROM {$wpdb->links}
+									WHERE link_owner = %d
+									LIMIT 1",
+									$delete_user->ID
+								)
+							) ) {
+								$user_has_content = true;
 							}
 						}
-
-						if ( '' === $user_list ) {
-							$user_list = $admin_out;
-						}
-
-						$user_dropdown .= $user_list;
-						$user_dropdown .= "</select>\n";
-						?>
-						<ul style="list-style:none;">
-							<li>
+						restore_current_blog();
+
+						if ( ! $user_has_content ) {
+							?>
+							<p>
+							<?php
+							/* translators: %s: Link to user's site. */
+							printf( __( 'Site: %s' ), $user_site );
+							?>
+							</p>
+							<input type="hidden" id="delete_option_<?php echo esc_attr( $details->userblog_id . '_' . $delete_user->ID ); ?>" name="delete[<?php echo $details->userblog_id . '][' . $delete_user->ID; ?>]" value="delete" required />
+							<p><?php _e( 'This user does not have any content.' ); ?></p>
+							<?php
+						} else {
+							?>
+							<fieldset>
+								<legend>
 								<?php
 								/* translators: %s: Link to user's site. */
 								printf( __( 'Site: %s' ), $user_site );
 								?>
-							</li>
-							<li><label><input type="radio" id="delete_option0" name="delete[<?php echo $details->userblog_id . '][' . $delete_user->ID; ?>]" value="delete" checked="checked" />
-							<?php _e( 'Delete all content.' ); ?></label></li>
-							<li><label><input type="radio" id="delete_option1" name="delete[<?php echo $details->userblog_id . '][' . $delete_user->ID; ?>]" value="reassign" />
-							<?php _e( 'Attribute all content to:' ); ?></label>
-							<?php echo $user_dropdown; ?></li>
-						</ul>
-						<?php
+								</legend>
+								<ul>
+									<li>
+										<input type="radio" id="delete_option_<?php echo esc_attr( $details->userblog_id . '_' . $delete_user->ID ); ?>" name="delete[<?php echo $details->userblog_id . '][' . $delete_user->ID; ?>]" value="delete" required />
+										<label for="delete_option_<?php echo esc_attr( $details->userblog_id . '_' . $delete_user->ID ); ?>"><?php _e( 'Delete all content.' ); ?></label>
+									</li>
+									<li>
+										<input type="radio" id="reassign_option_<?php echo esc_attr( $details->userblog_id . '_' . $delete_user->ID ); ?>" name="delete[<?php echo $details->userblog_id . '][' . $delete_user->ID; ?>]" value="reassign" required />
+										<label for="reassign_option_<?php echo esc_attr( $details->userblog_id . '_' . $delete_user->ID ); ?>"><?php _e( 'Attribute all content to another user.' ); ?></label>
+
+										<label for="reassign_user_<?php echo esc_attr( $details->userblog_id . '_' . $delete_user->ID ); ?>" class="screen-reader-text"><?php _e( 'Select a user to attribute the content to.' ); ?></label>
+										<?php
+										wp_dropdown_users(
+											array(
+												'show_option_none' => __( 'Select a user' ),
+												'name'    => "blog[$user_id][$key]",
+												'include' => $blog_users,
+												'show'    => 'display_name_with_login',
+												'id'      => "reassign_user_{$details->userblog_id}_{$delete_user->ID}",
+											)
+										);
+										?>
+
+									</li>
+								</ul>
+							</fieldset>
+							<?php
+						}
 					}
 				}
 				echo '</fieldset></td></tr>';
@@ -982,7 +1028,7 @@ function confirm_delete_users( $users ) {
 	</table>
 	<?php
 	/** This action is documented in wp-admin/users.php */
-	do_action( 'delete_user_form', $current_user, $allusers );
+	do_action( 'delete_user_form', $current_user, $users );
 
 	if ( 1 === count( $users ) ) :
 		?>
@@ -992,7 +1038,7 @@ function confirm_delete_users( $users ) {
 		<?php
 	endif;
 
-	submit_button( __( 'Confirm Deletion' ), 'primary' );
+	submit_button( __( 'Confirm Deletion' ), 'primary', 'submit', false, array( 'id' => 'confirm-users-deletion' ) );
 	?>
 	</form>
 	<?php
diff --git a/src/wp-admin/includes/user.php b/src/wp-admin/includes/user.php
index 255358b48afaa..df91be7e4b98e 100644
--- a/src/wp-admin/includes/user.php
+++ b/src/wp-admin/includes/user.php
@@ -562,26 +562,6 @@ function default_password_nag() {
 	);
 }
 
-/**
- * @since 3.5.0
- * @access private
- */
-function delete_users_add_js() {
-	?>
-<script>
-jQuery( function($) {
-	var submit = $('#submit').prop('disabled', true);
-	$('input[name="delete_option"]').one('change', function() {
-		submit.prop('disabled', false);
-	});
-	$('#reassign_user').focus( function() {
-		$('#delete_option1').prop('checked', true).trigger('change');
-	});
-} );
-</script>
-	<?php
-}
-
 /**
  * Optional SSL preference that can be turned on by hooking to the 'personal_options' action.
  *
diff --git a/src/wp-admin/network/users.php b/src/wp-admin/network/users.php
index 29238cd887034..3e18aae9673a4 100644
--- a/src/wp-admin/network/users.php
+++ b/src/wp-admin/network/users.php
@@ -56,8 +56,9 @@
 
 				$doaction     = $_POST['action'];
 				$userfunction = '';
+				$allusers     = (array) $_POST['allusers'];
 
-				foreach ( (array) $_POST['allusers'] as $user_id ) {
+				foreach ( $allusers as $user_id ) {
 					if ( ! empty( $user_id ) ) {
 						switch ( $doaction ) {
 							case 'delete':
@@ -72,7 +73,7 @@
 								require_once ABSPATH . 'wp-admin/admin-header.php';
 
 								echo '<div class="wrap">';
-								confirm_delete_users( $_POST['allusers'] );
+								confirm_delete_users( $allusers );
 								echo '</div>';
 
 								require_once ABSPATH . 'wp-admin/admin-footer.php';
@@ -188,6 +189,32 @@
 				wp_die( __( 'Sorry, you are not allowed to access this page.' ), 403 );
 			}
 
+			/*
+			 * Validate that every "reassign" choice has a real target before making
+			 * any changes. The confirmation form blocks this client-side, so this is
+			 * a defense-in-depth guard against an invalid reassignment (e.g. content
+			 * reassigned to the non-existent user "-1") when JavaScript is bypassed.
+			 * Bail out entirely so the deletion is all-or-nothing.
+			 */
+			if ( ! empty( $_POST['blog'] ) && is_array( $_POST['blog'] ) && ! empty( $_POST['delete'] ) ) {
+				foreach ( $_POST['blog'] as $id => $blogs ) {
+					foreach ( $blogs as $blogid => $reassign_user_id ) {
+						if ( isset( $_POST['delete'][ $blogid ][ $id ] )
+							&& 'reassign' === $_POST['delete'][ $blogid ][ $id ]
+							&& (int) $reassign_user_id < 1
+						) {
+							wp_redirect(
+								add_query_arg(
+									array( 'error' => 'missing_reassign' ),
+									network_admin_url( 'users.php' )
+								)
+							);
+							exit;
+						}
+					}
+				}
+			}
+
 			if ( ! empty( $_POST['blog'] ) && is_array( $_POST['blog'] ) ) {
 				foreach ( $_POST['blog'] as $id => $users ) {
 					foreach ( $users as $blogid => $user_id ) {
@@ -310,6 +337,17 @@
 		)
 	);
 }
+
+if ( isset( $_REQUEST['error'] ) && 'missing_reassign' === $_REQUEST['error'] ) {
+	wp_admin_notice(
+		__( 'No users were deleted because no user was selected for content reassignment.' ),
+		array(
+			'type'        => 'error',
+			'dismissible' => true,
+			'id'          => 'message',
+		)
+	);
+}
 ?>
 <div class="wrap">
 	<h1 class="wp-heading-inline"><?php esc_html_e( 'Users' ); ?></h1>
diff --git a/src/wp-admin/users.php b/src/wp-admin/users.php
index 650f81027592c..a94a9eff4a9cf 100644
--- a/src/wp-admin/users.php
+++ b/src/wp-admin/users.php
@@ -213,12 +213,17 @@
 				continue;
 			}
 
-			switch ( $_REQUEST['delete_option'] ) {
+			if ( 'reassign' === $_REQUEST['delete_option'][ $id ] && empty( $_REQUEST['reassign_user'][ $id ] ) ) {
+				$update = 'err_missing_reassign';
+				continue;
+			}
+
+			switch ( $_REQUEST['delete_option'][ $id ] ) {
 				case 'delete':
 					wp_delete_user( $id );
 					break;
 				case 'reassign':
-					wp_delete_user( $id, $_REQUEST['reassign_user'] );
+					wp_delete_user( $id, $_REQUEST['reassign_user'][ $id ] );
 					break;
 			}
 
@@ -306,40 +311,9 @@
 			$user_ids = array_diff( $user_ids, array( $current_user->ID ) );
 		}
 
-		/**
-		 * Filters whether the users being deleted have additional content
-		 * associated with them outside of the `post_author` and `link_owner` relationships.
-		 *
-		 * @since 5.2.0
-		 *
-		 * @param bool  $users_have_additional_content Whether the users have additional content. Default false.
-		 * @param int[] $user_ids                      Array of IDs for users being deleted.
-		 */
-		$users_have_content = (bool) apply_filters( 'users_have_additional_content', false, $user_ids );
-
-		if ( $user_ids && ! $users_have_content ) {
-			if ( $wpdb->get_var(
-				"SELECT ID FROM {$wpdb->posts}
-				WHERE post_author IN( " . implode( ',', $user_ids ) . ' )
-				LIMIT 1'
-			) ) {
-				$users_have_content = true;
-			} elseif ( $wpdb->get_var(
-				"SELECT link_id FROM {$wpdb->links}
-				WHERE link_owner IN( " . implode( ',', $user_ids ) . ' )
-				LIMIT 1'
-			) ) {
-				$users_have_content = true;
-			}
-		}
-
-		if ( $users_have_content ) {
-			add_action( 'admin_head', 'delete_users_add_js' );
-		}
-
 		require_once ABSPATH . 'wp-admin/admin-header.php';
 		?>
-		<form method="post" name="updateusers" id="updateusers">
+		<form method="post" name="updateusers" id="updateusers" class="delete-and-reassign-users-form">
 		<?php wp_nonce_field( 'delete-users' ); ?>
 		<?php echo $referer; ?>
 
@@ -365,7 +339,8 @@
 
 		<ul>
 		<?php
-		$go_delete = 0;
+		$go_delete          = 0;
+		$users_have_content = false;
 
 		foreach ( $all_user_ids as $id ) {
 			$user = get_userdata( $id );
@@ -385,12 +360,97 @@
 					'<input type="hidden" name="users[]" value="%s" />',
 					esc_attr( $id )
 				);
-				printf(
-					/* translators: 1: User ID, 2: User login. */
-					__( 'ID #%1$s: %2$s' ),
-					$id,
-					$user->user_login
-				);
+
+				/**
+				 * Filters whether the users being deleted have additional content
+				 * associated with them outside of the `post_author` and `link_owner` relationships.
+				 *
+				 * @since 5.2.0
+				 *
+				 * @param bool  $users_have_additional_content Whether the users have additional content. Default false.
+				 * @param int[] $user_ids                      Array of IDs for users being deleted.
+				 */
+				$user_has_content = (bool) apply_filters( 'users_have_additional_content', false, array( $id ) );
+
+				if ( ! $user_has_content ) {
+					if ( $wpdb->get_var(
+						$wpdb->prepare(
+							"SELECT ID FROM {$wpdb->posts}
+							WHERE post_author = %d
+							LIMIT 1",
+							$id
+						)
+					) ) {
+						$user_has_content = true;
+					} elseif ( $wpdb->get_var(
+						$wpdb->prepare(
+							"SELECT link_id FROM {$wpdb->links}
+							WHERE link_owner = %d
+							LIMIT 1",
+							$id
+						)
+					) ) {
+						$user_has_content = true;
+					}
+				}
+
+				if ( ! $user_has_content ) {
+					?>
+					<input type="hidden" name="delete_option[<?php echo esc_attr( $id ); ?>]" value="delete" required />
+					<p>
+					<?php
+					printf(
+						/* translators: 1: User login. 2: User ID */
+						__( '%1$s (ID #%2$s): This user does not have any content.' ),
+						'<strong>' . $user->user_login . '</strong>',
+						$id
+					);
+					?>
+					</p>
+					<?php
+				} else {
+					?>
+					<fieldset>
+					<legend>
+					<?php
+					printf(
+						/* translators: 1: User login, 2: User ID. */
+						__( '%1$s (ID #%2$s): What should be done with the content owned by this user?' ),
+						'<strong>' . $user->user_login . '</strong>',
+						$id
+					);
+					?>
+					</legend>
+
+					<ul>
+						<li>
+							<input type="radio" id="delete_option_<?php echo esc_attr( $id ); ?>" name="delete_option[<?php echo esc_attr( $id ); ?>]" value="delete" required />
+							<label for="delete_option_<?php echo esc_attr( $id ); ?>"><?php _e( 'Delete all content.' ); ?></label>
+						</li>
+						<li>
+							<input type="radio" id="reassign_option_<?php echo esc_attr( $id ); ?>" name="delete_option[<?php echo esc_attr( $id ); ?>]" value="reassign" required />
+							<label for="reassign_option_<?php echo esc_attr( $id ); ?>"><?php _e( 'Attribute all content to another user.' ); ?></label>
+
+							<label for="reassign_user_<?php echo esc_attr( $id ); ?>" class="screen-reader-text"><?php _e( 'Select a user to attribute the content to.' ); ?></label>
+							<?php
+							wp_dropdown_users(
+								array(
+									'show_option_none'  => __( 'Select a user' ),
+									'option_none_value' => '',
+									'name'              => 'reassign_user[' . $id . ']',
+									'id'                => 'reassign_user_' . $id,
+									'exclude'           => $user_ids,
+									'show'              => 'display_name_with_login',
+								)
+							);
+							?>
+						</li>
+					</ul>
+					</fieldset>
+					<?php
+					$users_have_content = true;
+				}
+
 				echo "</li>\n";
 
 				++$go_delete;
@@ -401,41 +461,6 @@
 
 		<?php
 		if ( $go_delete ) :
-
-			if ( ! $users_have_content ) :
-				?>
-				<input type="hidden" name="delete_option" value="delete" />
-			<?php else : ?>
-				<fieldset>
-				<?php if ( 1 === $go_delete ) : ?>
-					<p><legend><?php _e( 'What should be done with content owned by this user?' ); ?></legend></p>
-				<?php else : ?>
-					<p><legend><?php _e( 'What should be done with content owned by these users?' ); ?></legend></p>
-				<?php endif; ?>
-
-				<ul style="list-style:none;">
-					<li>
-						<input type="radio" id="delete_option0" name="delete_option" value="delete" />
-						<label for="delete_option0"><?php _e( 'Delete all content.' ); ?></label>
-					</li>
-					<li>
-						<input type="radio" id="delete_option1" name="delete_option" value="reassign" />
-						<label for="delete_option1"><?php _e( 'Attribute all content to:' ); ?></label>
-						<?php
-						wp_dropdown_users(
-							array(
-								'name'    => 'reassign_user',
-								'exclude' => $user_ids,
-								'show'    => 'display_name_with_login',
-							)
-						);
-						?>
-					</li>
-				</ul>
-				</fieldset>
-				<?php
-			endif;
-
 			/**
 			 * Fires at the end of the delete users form prior to the confirm button.
 			 *
@@ -612,10 +637,11 @@
 
 		$messages = array();
 		if ( isset( $_GET['update'] ) ) :
+			$delete_count = isset( $_GET['delete_count'] ) ? (int) $_GET['delete_count'] : 0;
+
 			switch ( $_GET['update'] ) {
 				case 'del':
 				case 'del_many':
-					$delete_count = isset( $_GET['delete_count'] ) ? (int) $_GET['delete_count'] : 0;
 					if ( 1 === $delete_count ) {
 						$message = __( 'User deleted.' );
 					} else {
@@ -695,14 +721,16 @@
 							'dismissible'        => true,
 						)
 					);
-					$messages[] = wp_get_admin_notice(
-						__( 'Other user roles have been changed.' ),
-						array(
-							'id'                 => 'message',
-							'additional_classes' => array( 'updated' ),
-							'dismissible'        => true,
-						)
-					);
+					if ( $delete_count > 0 ) {
+						$messages[] = wp_get_admin_notice(
+							__( 'Other user roles have been changed.' ),
+							array(
+								'id'                 => 'message',
+								'additional_classes' => array( 'updated' ),
+								'dismissible'        => true,
+							)
+						);
+					}
 					break;
 				case 'err_admin_del':
 					$messages[] = wp_get_admin_notice(
@@ -713,14 +741,36 @@
 							'dismissible'        => true,
 						)
 					);
+					if ( $delete_count > 0 ) {
+						$messages[] = wp_get_admin_notice(
+							__( 'Other users have been deleted.' ),
+							array(
+								'id'                 => 'message',
+								'additional_classes' => array( 'updated' ),
+								'dismissible'        => true,
+							)
+						);
+					}
+					break;
+				case 'err_missing_reassign':
 					$messages[] = wp_get_admin_notice(
-						__( 'Other users have been deleted.' ),
+						__( 'Users could not be deleted because no user was selected for content reassignment.' ),
 						array(
 							'id'                 => 'message',
-							'additional_classes' => array( 'updated' ),
+							'additional_classes' => array( 'error' ),
 							'dismissible'        => true,
 						)
 					);
+					if ( $delete_count > 0 ) {
+						$messages[] = wp_get_admin_notice(
+							__( 'Other users have been deleted.' ),
+							array(
+								'id'                 => 'message',
+								'additional_classes' => array( 'updated' ),
+								'dismissible'        => true,
+							)
+						);
+					}
 					break;
 				case 'remove':
 					$messages[] = wp_get_admin_notice(