Connacht centre Dave McSharry has been forced after suffering a number of concussion injuries.
The 26-year-old said he was “devastated” at having to retire but was left with no choice following advice from a neurologist.
“Although I am devastated that my time as a player has come to an end, I know that it is the only decision available to me after speaking to the specialist,” he said in a statement. “I have thoroughly enjoyed my time as a professional rugby player with Connacht Rugby.
McSharry joined Connacht in 2011 and went on to play 65 times for the province. He was part of some memorable victories including the Heineken Cup win away to Toulouse in December 2013.
He won an Ireland A cap in January 2013, starting for the Wolfhounds side against England Saxons in Galway.
McSharry was called into Ireland's Six Nations training squad the following day but injury restricted his international progress that season.
Connacht Rugby Head Coach Pat Lam said: “While we are sad to see him moving on from the set up here, Dave’s health comes first and it is a reminder to all of us that rugby is only a small part of our life journey.
“Dave has achieved a lot in his career and I know that he will go on to achieve in other aspects of his life now.”