London Irish have officially confirmed that Sean O'Brien will join the club from Leinster after the 2019 World Cup, according to www.independent.ie.
The flanker will join the Premiership side in December 2019, bringing to an end his time with Leinster and Ireland. The 31-year-old, who turns 32 on Thursday, has played for his home province 122 times as well as winning 54 Ireland caps.
He has signed a three-season deal with London Irish, where he will link up with Director of Rugby Declan Kidney and head coach Les Kiss, who previously coached O'Brien with the Ireland team.
Speaking about the move, O'Brien stressed that it wasn't an easy choice to end his career in Ireland.
"This is one of the hardest decisions that I have ever had to make," O'Brien said.
"I have played all my rugby in Ireland.
"With Tullow, with Leinster and with Ireland and to move from the place I call home and that I love so much, was not easy.
"That being said, I feel that the time has come to explore other opportunities, to challenge myself at a new environment, in a new city, with a new club and against different players and teams on a weekly basis.
"London Irish and what they are about is a club that I feel I can grow with and also contribute to and I feel that they have a set up and an ethos that will make me feel at home.
"For me and the time I have left here in Ireland, I want to stay fit and healthy and finish out the season with a strong Six Nations with Ireland and then turn my attention to Leinster and hopefully a seat on the plane to Japan.
"Thanks to my family, friends and my girlfriend Sarah for their unbelievable support in making this decision and of course the fans for all the support I’ve received over the past 13 years.
"I am looking forward to representing Leinster and Ireland as best as I can over the next nine months."