In your theme’s functions.php, add the following code:
<?php add_filter( 'woocommerce_get_catalog_ordering_args', 'wcs_get_catalog_ordering_args' ); function wcs_get_catalog_ordering_args( $args ) { $orderby_value = isset( $_GET['orderby'] ) ? woocommerce_clean( $_GET['orderby'] ) : apply_filters( 'woocommerce_default_catalog_orderby', get_option( 'woocommerce_default_catalog_orderby' ) ); if ( 'on_sale' == $orderby_value ) { $args['orderby'] = 'meta_value_num'; $args['order'] = 'DESC'; $args['meta_key'] = '_sale_price'; } return $args; } add_filter( 'woocommerce_default_catalog_orderby_options', 'wcs_catalog_orderby' ); add_filter( 'woocommerce_catalog_orderby', 'wcs_catalog_orderby' ); function wcs_catalog_orderby( $sortby ) { $sortby['on_sale'] = 'On Sale'; return $sortby; }
Note: you can replace the On Sale text.
Source: https://metorik.com/blog/order-products-by-on-sale-in-woocommerce