William's mbuna (Maylandia greshakei), also known as ice blue zebra mbuna or ice blue zebra or the Pseudotropheus ice blue among the aquarium enthusiasts, is a species of cichlid fish endemic to Lake Malawi where it is only found at Makokola in the southeastern arm of the lake. This species can reach a length of 13.4 centimetres (5.3 in) TL. It can also be found in the aquarium trade. The specific name honours the German ornamental fish importer Alfons Greshake.