The B class were a class of diesel locomotives built by Commonwealth Engineering for the Western Australian Government Railways between 1962 and 1965.

The first five B class units entered service in 1962.

Three years later, a second batch of five was delivered.

[1] The second batch differed from the first only in having sloping cab sides, to enable the second batch to pass underneath the limited clearance cranes on the Fremantle wharves.

[1] All members of the class spent the whole of their working lives in the Perth metropolitan area, and were written off as a group in September 1984.