The man was injured after he hit the railing while cycling on College Avenue in Mountmellick at around 4.30pm yesterday afternoon.
The cyclist was brought to the Midland Regional Hospital, Portlaoise, where he passed away last night.
Gardaí are appealing to witnesses, particularly drivers with dash cam footage who were travelling in thast area at the time to contact Portlaoise Garda Station on 057 867 4100, the Garda Confidential Line on 1800 666 111, or any garda station.
The cyclist was the second person to die on Irish roads yesterday.
It was reported last night that a man in his 30s has died following a crash involving a tractor in Co Cavan. The man driving the tractor was pronounced dead on the scene.
The drivers body was taken to Cavan Monaghan General Hospital where a post mortem exam is due to take place.
Gardaí are appealing to any witnesses who may have dash cam footage and were travelling in the area between 9am and 12.40pm, to contact Cavan Garda Station on 049 436 8800, the Garda Confidential Line on 1800 666 111, or any garda station.
