The War Department (WD) "Austerity" 2-8-0 is a type of heavy freight steam locomotive that was introduced in 1943 for war service. A total of 935 were built, making this one of the most-produced classes of British steam locomotive. They were nicknamed Ozzies by the railwaymen.

The Austerity 2-8-0 was based on the LMS Class 8F, which until that point had been the government's standard design. Various modifications were made to the 8F design by Robert Riddles in order to prioritise low cost over design life. 

After the end of the conflict, the War Department disposed of 930 locomotives (Two engines being retained by the War Department and three being scrapped). 200 were sold to the LNER, which classified them as "Class O7" and numbered them 3000–3199. In 1948, 533 more were purchased by the British Transport Commission. With the formation of British Railways, the 733 locomotives were renumbered into the 90000–90732 series.

One WD 2-8-0 has survived. Vulcan Foundry works No. 5200 was repatriated from Sweden to the Keighley and Worth Valley Railway. It was SJ Class G11 number 1931. It was overhauled to its original condition, finished in 2007, which involved building a new cab and tender, to become BR "No. 90733". After test runs, 90733 ran its first passenger train on Monday 23 July 2007.