diff --git a/autoload.php b/autoload.php
index 30ec1d7c1b8..ce69ecd8a1b 100644
--- a/autoload.php
+++ b/autoload.php
@@ -1190,6 +1190,7 @@ $wgAutoloadLocalClasses = [
 	'RecentChange' => __DIR__ . '/includes/changes/RecentChange.php',
 	'RecentChangesUpdateJob' => __DIR__ . '/includes/jobqueue/jobs/RecentChangesUpdateJob.php',
 	'RecompressTracked' => __DIR__ . '/maintenance/storage/recompressTracked.php',
+	'RecountCategories' => __DIR__ . '/maintenance/recountCategories.php',
 	'RedirectSpecialArticle' => __DIR__ . '/includes/specialpage/RedirectSpecialPage.php',
 	'RedirectSpecialPage' => __DIR__ . '/includes/specialpage/RedirectSpecialPage.php',
 	'RedisBagOStuff' => __DIR__ . '/includes/libs/objectcache/RedisBagOStuff.php',
diff --git a/maintenance/recountCategories.php b/maintenance/recountCategories.php
new file mode 100644
index 00000000000..a4bfa989921
--- /dev/null
+++ b/maintenance/recountCategories.php
@@ -0,0 +1,172 @@
+<?php
+/**
+ * Refreshes category counts.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup Maintenance
+ */
+
+require_once __DIR__ . '/Maintenance.php';
+
+use MediaWiki\MediaWikiServices;
+
+/**
+ * Maintenance script that refreshes category membership counts in the category
+ * table.
+ *
+ * (The populateCategory.php script will also recalculate counts, but
+ * recountCategories only updates rows that need to be updated, making it more
+ * efficient.)
+ *
+ * @ingroup Maintenance
+ */
+class RecountCategories extends Maintenance {
+	public function __construct() {
+		parent::__construct();
+		$this->addDescription( <<<'TEXT'
+This script refreshes the category membership counts stored in the category
+table. As time passes, these counts often drift from the actual number of
+category members. The script identifies rows where the value in the category
+table does not match the number of categorylinks rows for that category, and
+updates the category table accordingly.
+
+To fully refresh the data in the category table, you need to run this script
+three times: once in each mode. Alternatively, just one mode can be run if
+required.
+TEXT
+		);
+		$this->addOption(
+			'mode',
+			'(REQUIRED) Which category count column to recompute: "pages", "subcats" or "files".',
+			true,
+			true
+		);
+		$this->addOption(
+			'begin',
+			'Only recount categories with cat_id greater than the given value',
+			false,
+			true
+		);
+		$this->addOption(
+			'throttle',
+			'Wait this many milliseconds after each batch. Default: 0',
+			false,
+			true
+		);
+
+		$this->setBatchSize( 500 );
+	}
+
+	public function execute() {
+		$this->mode = $this->getOption( 'mode' );
+		if ( !in_array( $this->mode, [ 'pages', 'subcats', 'files' ] ) ) {
+			$this->error( 'Please specify a valid mode: one of "pages", "subcats" or "files".', 1 );
+		}
+
+		$this->minimumId = intval( $this->getOption( 'begin', 0 ) );
+
+		// do the work, batch by batch
+		$affectedRows = 0;
+		while ( ( $result = $this->doWork() ) !== false ) {
+			$affectedRows += $result;
+			usleep( $this->getOption( 'throttle', 0 ) * 1000 );
+		}
+
+		$this->output( "Done! Updated the {$this->mode} counts of $affectedRows categories.\n" .
+			"Now run the script using the other --mode options if you haven't already.\n" );
+		if ( $this->mode === 'pages' ) {
+			$this->output(
+				"Also run 'php cleanupEmptyCategories.php --mode remove' to remove empty,\n" .
+				"nonexistent categories from the category table.\n\n" );
+		}
+	}
+
+	protected function doWork() {
+		$this->output( "Finding up to {$this->mBatchSize} drifted rows " .
+			"starting at cat_id {$this->minimumId}...\n" );
+
+		$countingConds = [ 'cl_to = cat_title' ];
+		if ( $this->mode === 'subcats' ) {
+			$countingConds['cl_type'] = 'subcat';
+		} elseif ( $this->mode === 'files' ) {
+			$countingConds['cl_type'] = 'file';
+		}
+
+		$dbr = $this->getDB( DB_REPLICA, 'vslow' );
+		$countingSubquery = $dbr->selectSQLText( 'categorylinks',
+			'COUNT(*)',
+			$countingConds,
+			__METHOD__ );
+
+		// First, let's find out which categories have drifted and need to be updated.
+		// The query counts the categorylinks for each category on the replica DB,
+		// but this data can't be used for updating the master, so we don't include it
+		// in the results.
+		$idsToUpdate = $dbr->selectFieldValues( 'category',
+			'cat_id',
+			[
+				'cat_id > ' . $this->minimumId,
+				"cat_{$this->mode} != ($countingSubquery)"
+			],
+			__METHOD__,
+			[ 'LIMIT' => $this->mBatchSize ]
+		);
+		if ( !$idsToUpdate ) {
+			return false;
+		}
+		$this->output( "Updating cat_{$this->mode} field on " .
+			count( $idsToUpdate ) . " rows...\n" );
+
+		// In the next batch, start where this query left off. The rows selected
+		// in this iteration shouldn't be selected again after being updated, but
+		// we still keep track of where we are up to, as extra protection against
+		// infinite loops.
+		$this->minimumId = end( $idsToUpdate );
+
+		// Now, on master, find the correct counts for these categories.
+		$dbw = $this->getDB( DB_MASTER );
+		$res = $dbw->select( 'category',
+			[ 'cat_id', 'count' => "($countingSubquery)" ],
+			[ 'cat_id' => $idsToUpdate ],
+			__METHOD__ );
+
+		// Update the category counts on the rows we just identified.
+		// This logic is equivalent to Category::refreshCounts, except here, we
+		// don't remove rows when cat_pages is zero and the category description page
+		// doesn't exist - instead we print a suggestion to run
+		// cleanupEmptyCategories.php.
+		$affectedRows = 0;
+		foreach ( $res as $row ) {
+			$dbw->update( 'category',
+				[ "cat_{$this->mode}" => $row->count ],
+				[
+					'cat_id' => $row->cat_id,
+					"cat_{$this->mode} != {$row->count}",
+				],
+				__METHOD__ );
+			$affectedRows += $dbw->affectedRows();
+		}
+
+		MediaWikiServices::getInstance()->getDBLoadBalancerFactory()->waitForReplication();
+
+		return $affectedRows;
+	}
+}
+
+$maintClass = 'RecountCategories';
+require_once RUN_MAINTENANCE_IF_MAIN;