The class H of the Federated Malay States Railway refers to a total of 60 light, meter-gauge Pacifics. The first seven were built by Kitson from November 1906. Others followed from Nasmyth, Wilson & Co., six of which went to the Johore State Railway. While the latter were also handed over to the FMSR, further series were created by Kitson and Robert Stephenson.
Since the later deliveries were somewhat heavier due to stronger frames and had further differences in details, the three series were subsequently named H1, H2 and H3. The H1 were withdrawn between 1929 and 1934. Of the newer machines, many were classified as class 501 by the Malayan Railways in 1946. 