The Olympic mudminnow (Novumbra hubbsi) is a fish native to the western lowlands of Washington: the Chehalis River basin, Deschutes River basin, and some Olympic Peninsula basins. It grows to 8 cm (about 3 in) in length, and is Washington's only known endemic freshwater fish species. Although they strongly resemble killifish, mudminnows are more closely related to pike and muskellunge.