The Sri Lanka Railways M4 is a class of diesel-electric locomotive manufactured in Canada by Montreal Locomotive Works. Fourteen of the manufacturers' model MX-620 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 rarely used beyond Polgahawela on the main line (only with assistance from a dynamic brakes equipped locomotive on downhill), and are not used beyond Nawalapitiya. They used to travel on the full main line regularly until the previous decade.

They are painted in a livery of dark blue, light blue, silver with yellow striping; although No. 752 Point Pedro was painted in a special ICE (Intercity Express) livery.

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  Class M4 No. 745 "Ruwanveli"
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  Class M4 No. 748 "Walawe"
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  M4 No. 749 "Dunhida"
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  Class M4 No. 754 "Menik"
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  Class M4 No. 755 "Mahaweli"
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  Class M4 No. 756 "Laxapana"

• "Class M4 Locomotive". www.ceylonrailway.com.
• Hughes, Hugh (1996). Indian Locomotives: Part 4 – 1941–1990. Harrow, Middlesex: The Continenetal Railway Circle. ISBN 0-9521655-1-1.