The ex-Leinster and Lion back row announced his retirement this morning.
Sean O'Brien is retiring from professional rugby at the end of this season.
The former Leinster back row, who won 56 caps for Ireland and also toured with the Lions, has been playing at London Irish.
In his post to Instagram this morning announcing his retirement at the end of the season; O'Brien mentioned former president, player, coach, rep and player as being an influence in the initial phase of his career.
"I would like to say a special thank you to to some people who believed in me early on in my career, who are sadly no longer with us. Jim Kealy (Tullow RFC) and David Wilkie (Edenderry RFC) always said the right thing and gave me direction when needed."
Speaking to leinsterrugby.ie this morning, Leinster Rugby head coach Leo Cullen said,
"Seán will be remembered as one of the very special Leinster players, particularly his performances in helping Leinster win the Heineken Cup in 2011 and 2012.
"He was a fearless competitor and he gave incredible confidence to those around him.
"Seán also made a huge impact at grassroots level where he has done so much great work in helping grow the game and inspiring so many young players to believe that anything was possible.
"On behalf of everyone at Leinster Rugby, we would like to wish Seán every success in the future as he takes on new challenges in the next stage of his life.”
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