The class K of the Western Australian Government Railways designates 24 2-8-4T tank locomotives built by Neilson & Co. between 1893 and 1898. The class name was taken over from a single 0-6-2T locomotive built in 1891 that had been renamed to class L. After being operated on the Eastern Railway, it only took until 1902 for them to be replaced there by the 4-8-0 class F tender locomotive. After this they operated around Perth and Collie.

Between 1915 and 1929, six received a superheated boiler and were now called class Ks. Although these boilers increased power, also due to their higher pressure, they had all again been switched back for saturated boilers by 1937. An interesting fact is that No. 34 got its superheated boiler in 1929, at a time when multiple others had already been rebuilt back.

Some had already been withdrawn in 1927 and 1928, but most were still in service at the beginning of the fifties. No. 190 was the last one and was withdrawn on December 7, 1964. Six identical locomotives built in 1900 had also been planned to be delivered to the WAGR, but were bought by the British Government instead. Then they were supplied to the Imperial Military Railways in South Africa, soon becoming CSAR class C.