The man's bike was struck by an Asda articulated lorry on the A82 at Dunochter at about 11.00 on Sunday.
The incident happened on the west bound carriageway between the Kilbowie roundabout and the Erskine Bridge. The cyclist was pronounced dead at the scene.
The west bound carriageway was closed with diversions in place. Police have appealed for witnesses.
Sgt Archie McGuire of Police Scotland said: "Inquiries are at an early stage to establish the exact circumstances of this incident and it is essential that any witnesses come forward as soon as possible.
"I would like to speak to anyone who was on the A82 around 1100 hours this morning, particularly those travelling on the east bound carriageway, who may have seen what happened.
"I would also like to see any footage of the incident which may have been captured on a dash cam or by any local businesses or properties with CCTV."
A cyclist has died after being hit by a lorry in West Dunbartonshire.