The incident happened just after midnight at Grange Lake on the river Shannon near Strokestown.
A 34 year old woman – who was a passenger in the car – survived the crash.
Gardaí in Boyle say they're investigating all of the circumstances surrounding the man's death – but at this stage it's believed to be a tragic accident.
The man's body has been removed to Roscommon County Hospital for a post mortem examination.
