A motorcyclist was taken to Tallaght Hospital following the two-vehicle collision.
Gardaí are appealing for witnesses to a serious crash in Offaly over the weekend.
A two-vehicle collision - involving car and a motorcycle - occurred on the N62 at Boveen, Birr at about 6 o'clock on Saturday evening.
The motorcyclist, a man in his 50s, was later taken to Tallaght Hospital, where he is receiving treatment for serious injuries.
Gardaí are appealing for any road users who were travelling on this road at the time to come forward, particularly those with dash cam footage.
Anyone with information is asked to contact Birr Garda station on 057 9169710, the Garda Confidential Line on 1800 666 111 or any Garda station.