The Sri Lanka Railways M4 is a class of diesel-electric locomotive manufactured in Canada by Montreal Locomotive Works. Fourteen of the manufacturers' model were imported in 1975. This was the longest locomotive in the Sri Lanka Railways previously. All units are still operational. On regular operation they are not used beyond Polgahawela on the main line, and are not used on the hill country section. They used to travel on the full main line regularly until the previous decade.