The Metropolitan Railway A Class and B Class were 4-4-0T condensing steam locomotives built for the Metropolitan Railway by Beyer Peacock, first used in 1864. A total of 40 A Class and 26 of the slightly different B Class were delivered by 1885. Used underground, the locomotives condensed their steam, and coke or smokeless coal was burnt to reduce the smoke.

Most locomotives were withdrawn after electrification in the early 20th century, forty having been sold by 1907.