Darwin's Galápagos mouse is a rodent known from records on Santa Cruz Island in the Galápagos.
Its coat is described as reddish brown and streaked with darker hairs, and its tail is short relative to its body.
The last known specimens were collected in April 1930.
The underparts are reddish brown, with grey bases to the hairs.
Total length, including the tail, is 204–222 mm.
An extinction-risk assessment has not been added yet.