Stygimys is an extinct mammal genus from the Upper Cretaceous and Paleocene of North America.

It was a member of the extinct order Multituberculata within the suborder Cimolodonta, family Eucosmodontidae.

Place: Puercan (Paleocene)-age strata of Rav W-1 in Saskatchewan, Canada.

Remains are known from the Puercan (Paleocene)-age strata of the Long Fall Horizon of Canada.

The species Stygimys jepseni was named by George Gaylord Simpson in 1935 and Sloan and Van Valen in 1965.

Remains are known from the Torrejonian (Paleocene)-age strata of the San Juan Basin of New Mexico.