Wales centre Scott Williams is to leave Scarlets at the end of the season and join their Welsh regional rivals Ospreys.
The PRO14 side confirmed that Williams has agreed a three-year deal and will link up with them next summer.
"I hope it goes without saying that this has not been an easy decision for me, but ultimately, I feel it is a move that is the right option for me at this time in my career," Williams said in a statement released by Ospreys.
"I've loved every minute of my 11 years at the Scarlets. I will always be grateful to the board, [Scarlets head coach] Wayne [Pivac] and his team, and all associated with the club, for their support over those years.
The 27-year-old won his 50th Test cap when Wales were beaten by New Zealand last weekend, and is now preparing himself for a "fresh challenge" with the Ospreys.
"I am now looking forward to a fresh challenge at the Ospreys," he continued.
"I'm excited about the their mid and long-term plans and goals, and my role there as a senior player. I hope it will allow me to continue improving and developing, both as a player and as a person, which is a great motivator for me."
Ospreys head coach Steve Tandy added: "Scott is a quality player who has consistently delivered at the highest level of the game and would be a welcome addition to any squad.
"He is someone we have admired for some time, a leader who has captained Wales and the Scarlets, and he is the kind of signing that excites supporters.
"For us to secure his signature in the face of real competition is a significant statement of intent about what we are trying to do at the Ospreys and our ambition to ensure we can continue to compete at the top end."
Williams made his Scarlets debut in 2010, before making a first Wales appearance the following year and going on to be part of two successive World Cup campaigns.
Scarlets general manager Jon Daniels said: "Negotiations to retain Scott have been ongoing for some months, but today we can confirm he will be leaving us at the end of the season.
"Sometimes, despite everyone's best efforts, a player decides the next chapter of his rugby career should be at another club.
"We would like to thank Scott for his services to the Scarlets, not only as a player, but also as vice-captain and captain, leading the club with pride."
Ospreys' Samoa international centre Kieron Fonotia, meanwhile, will head in the opposite direction next term when he links up with Scarlets.