Ulster have announced that Leinster loose-head Jack McGrath will join the province in the summer.
The Lions prop will swap Dublin for Belfast saying the move will put him "in the best position to continue to perform at the top end of the game".
McGrath has seen fallen behind Cian Healy as the starting loose-head for both Leinster and Ireland this season.
Commenting on the switch, McGraht said: "This was a difficult decision but one I believe will put me in the best position to continue to perform at the top end of the game.
I have enjoyed a huge amount of success at Leinster, but I feel that looking beyond the World Cup to the next phase of my career, I will benefit from the opportunity within the Ulster environment.
“I am now fully fit after a disrupted start to the season and I’m looking forward to putting all my energy into helping Leinster’s drive to defend the European and PRO14 titles and finishing this season on a high."
Ulster boss Dan McFarland welcomed the move saying the province is "delighted" to have the 54 times capped prop coming on board.
"It is hugely encouraging to see a player of his calibre express the desire to join us, said McFarland.
"Jack’s quality on the field is undoubtable, and his experience of playing at the highest level will be a hugely valuable asset to the club as we continue to develop a promising group of young forwards."
Ulster suffered a narrow defeat to Leinster at the weekend,
McGrath however, was not in the matchday squad for the game with Cian Healy starting and Ed Byrne filling in on the bench.
Commenting on the switch, IRFU Performance Director David Nucifora said: "Jack has made a very tough decision which he believes will advance his case for selection for Ireland. You have to respect a player with such ambition.
"Leinster is a fantastic environment but it is testament to the work that all four provinces are doing that players are seeking opportunities within Ireland to advance their international careers."
McGrath has enjoyed considerable success for Leinster, winning three Champions Cups, a Pro14 title, two Pro12 titles and a Challenge Cup.
The 29-year-old joins a number of former Leinster players at the province, with Jordi Murphy, Marty Moore and John Cooney all currently lining out for Ulster.
Speaking to leinsterrugby.ie, Leinster head coach Leo Cullen praised McGrath for his part in the province's success since he made his debut in 2010.
Cullen said McGrath "is one of our most decorated players representing not only Leinster, but also Ireland and the British & Irish Lions with distinction."
He added: "We understand that this was not an easy decision for Jack to make but we wish him the very best for his future in the game and beyond that.
"Before that though we expect Jack to play a very important role for the remainder of the season as we continue to fight in two competitions."