The WAGR class G was a mixed-traffic locomotive designed by Beyer, Peacock & Co. and built by this company and three others. Of these, the Australian company of James Martin & Co. was the only one that was not from Britain. These locomotives were very similar to the Silverton Tramway class Y, the South Australian Railways class Y and Tasmanian Government Railways class C.

The first 48 were built from 1889 with the wheel arrangement 2-6-0. After it was found that the running characteristics with the leading Bissel axle were not always good, it was replaced with a two-axle bogie. So 24 more locomotives were built as 4-6-0. In World War II, 13 were sold to Commonwealth Railways and designated class NGA and NFC. Already at the beginning of the century, others had been sold to companies in the mining and timber industry. No. 71 of Millars was the last steam locomotive in revenue service in Western Australia when it was withdrawn in 1972. Five have been preserved, but only one is still in working order.