Emergency services were called to the Beinn Dearg peak in the Highlands at about 1.45pm on Saturday after reports that a man had collapsed.
Police, Dundonnell Mountain Rescue and a Coastguard helicopter attended the scene. Attempts were made to revive the victim but he died.
Police said no further details of the man would be released until his next of kin have been informed.
Beinn Dearg, in the Inverlael area, is the highest peak on the popular four Munros circuit.