Ashy Storm-petrel occur on the islands in the northeast Pacific off the coast of California and - to a lesser extent - northwestern Mexico. The largest number of them are on the Farallon Islands (off San Francisco), others are found on San Miguel Island, Santa Cruz Island, Anacapa Island, Santa Barbara Island, Santa Catalina Island and San Clemente Island. A small population nests on Mexico's Coronados.
Plumage is sooty-brown. The tail is forked.
It resembles the Black Storm-petrel, except for its smaller size.