The deepwater sculpin (Myoxocephalus thompsonii) is a species of freshwater fish in the family Cottidae of order Scorpaeniformes.

[2][1] It is a glacial relict, native to a limited number of deep, cold lakes in Canada and the United States.

[5] The description was based on specimens obtained by Spencer Fullerton Baird for the Smithsonian Institution from the stomachs of Burbot caught by fishermen on Lake Ontario.

[3] The deepwater sculpin is a small fish on average between 51–76 millimetres (2.0–3.0 in) in length[3] Its body is generally flattened in shape and tapers from the head to the tail.

[3] The deepwater sculpin feeds primarily on small crustaceans[2] Mysis diluviana and Diporeia.

[3][4] The deepwater sculpin is classified as of Least Concern by the IUCN based on the apparent stability of the population.

Threats include habitat loss, lake eutrophication, invasive species, and water pollution.