Ireland centre Robbie Henshaw will join Leinster on a three-year deal from Connacht this summer.
The deal will keep 22-year-old Henshaw in Ireland until after the 2019 Rugby World Cup in Japan.
"I would like to thank Connacht Rugby, the IRFU and Leinster for allowing me time to consider my future," Henshaw said in a statement on the official Irish Rugby Football Union website.
"This has been a long and difficult process and while I am sorry to be leaving Connacht I look forward to the next chapter of my rugby career at Leinster.
"The support I have enjoyed from the fans in the Sportsground and throughout the province is something that I really value, and I want to thank them for four great years."
Henshaw made his Connacht debut in 2012 and won his first Test cap as a full-back against the United States on Ireland's 2013 summer tour of North America.
He won his 17th cap in the 10-9 RBS 6 Nations defeat to France in Paris last weekend.
Leinster head coach Leo Cullen said: "We are delighted to have secured Robbie's signature for the next three seasons.
"Robbie is a huge talent and we have all seen that over the last few weeks and months with Ireland in the Six Nations and during the World Cup.
IRFU performance director David Nucifora said: "I am disappointed for Connacht that Robbie has decided to leave but pleased for Irish rugby that he has committed to a further three years.
"I know that the decision Robbie has taken to move from Connacht is not one he has taken lightly."