Ceylon Government Railway S1 was a class of Diesel multiple unit train sets built by English Electric for the Ceylon Government Railway.
Their inaugural run from Colombo Fort Station to Galle took place on 25 February 1938.
They served the Ceylon Government Railway for around 19 years before being withdrawn and scrapped in 1955.
Later that year, two diesel locomotives classified as the Class M3 Nos.
589 and 590 were built locally using the prime movers of the scrapped S1 sets.