Former Ireland and Leinster forward Seán O'Brien will retire from rugby at the end of the season.

The 35-year-old back-row won 56 caps for Ireland and was part of the Six Nations-winning side of 2015, while he also played in five Tests for the British and Irish Lions during their tours of Australia and New Zealand, in 2013 and 2017 respectively.

O’Brien is currently in his third season with London Irish, who he joined from Leinster in 2019 after 11 seasons with his home province.

The Carlow native won four European Cups, four Pro12/14 titles with Leinster and was named ERC European Player of the Year in 2011.

O'Brien and Johnny Sexton after Ireland's Six Nations win in 2015

"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," said O’Brien.

"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."

O'Brien scores a try in Leinster's European Cup final win over Ulster in 2012

O'Brien played 126 times for Leinster, scoring 20 tries, and his former team-mate Leo Cullen says he will be remembered as "one of the very special Leinster players".

The Leinster head coach said: "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."