The Tullow Tank is calling time on his playing career at the end of this season.
Now 35, Seán O'Brien will hang up his boots with London Irish in a few weeks time, bringing to a close a sparkling 14-year career at club and Test level.
The Carlow-born flanker made his Leinster debut in September 2008 and won four Heineken Champions Cups with his province, starting in the 2011 and '12 finals. He was named European player of the year in 2011.
O'Brien also won a European Challenge Cup with Leinster and five League crowns before, having made 126 appearances, moving to London Irish in 2019 to link up again with Declan Kidney, who was one of his head coaches during his time with Ireland.
He won a Six Nations title with Ireland in 2015 and made 56 appearances in green but O'Brien would have won many more caps for club and country only for a number of serious injuries, including shoulder issues that could have ended his career.
He was also an integral driving force on two Lions tours, in 2013 to Australia and 2017 to New Zealand.
"After much deliberation and consultation with my family and friends, I can confirm that I have decided to retire from playing professional rugby at the end of the season," said O'Brien.
"I’ve had an incredible career and am thankful for every second of my time at Leinster, Ireland, London Irish and the British and Irish Lions.
"As a 20-year-old, I fulfilled my childhood dream by pulling on the Leinster jersey, and when I made my debut against Cardiff Blues in 2008, I never imagined what would then follow over the next 14 years. A special mention must go to Colin McEntee for his ‘big brother’ approach when I joined the academy.
"I feel lucky to have experienced so many wonderful highlights over the course of my career.
"At an international level, I feel privileged to have won 56 caps for Ireland. I gave everything I could possibly give, and I will always look back with great pride at every time I pulled on the Irish jersey to represent my country, my county, my friends and family.
"I feel very fortunate to have had the career I've had but none of it would have been possible without the support of so many people.
"Firstly, I would like to thank my Mam and Dad for taking me to Ballon Rathoe Community Games and then Tullow RFC when I was eight years old.
"They took me to every sport in my area which gave me the exposure to all types of sport. They were the perfect role models who taught me to not be afraid of hard work, which certainly helped me progress my career. I can’t thank them enough.
"I was lucky to play alongside some great players and under some brilliant managers and coaches during my time at Tullow, Leinster, Ireland, London Irish and the Lions and I would like to thank every one of them.
"I would also like to thank the backroom staff at each of those clubs, they all showed me fantastic support during my time with them.
"I would like to say a special thank you 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 to me and gave me direction when needed.
"Away from rugby, I feel lucky to have had such a close group of friends that I have always been able to count and rely on throughout the course of my career. Thanks to all of you, especially James Foley and Daniel Davey.
"Finally, the most important thank you is reserved for my family. I can’t thank my Mum, Dad, brothers (Stephen and William) and sisters (Caroline and Alex) enough for their unconditional support over the years. It has meant everything to me and to have six nephews watching means the world to me.
"There is still a lot of rugby to be played this season before the time comes to hang up my boots, and I am fully focused on giving my all in the London Irish jersey until then. I’m going to soak up every minute I get on the pitch and look forward to helping the team wherever I can.
"I am excited about the future and feel I still have a lot to offer the game, in whatever capacity that may be. I am currently taking my time to consider a number of options and will make an announcement with regards to the next stage of my career very soon."
Leinster head coach Leo Cullen, who played alongside O'Brien at provincial and Test level, paid tribute to his former team-mate.
"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," said Cullen.
"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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