Gardai are appealing to anyone in Rathangan, who may have witnessed a serious assault, to come forward.
A 19-year-old man was getting into a taxi on Main Street at around 1.30am on December 27th when he was assaulted by another male.
The force of that punch caused him to fall backwards and hit the roadway.
He was taken by ambulance to Naas General Hospital where he is described as being in a serious condition.
A female was also assaulted, and sustained minor injuries during the incident.
The scene was preserved, and has undergone forensic examination.
No arrests have been made.
Gardai are asking anyone in the area at the time, in particular, drivers who may have dash-cams, to contact
Gardaí at Kildare 045-527730, the Garda Confidential Line 1800 666 111 or any Garda Station.