Wales centre Scott Williams is to leave the Scarlets and join regional rivals the Ospreys.
Williams has agreed a three-year deal, the Ospreys said.
He will link up with them next summer.
The 27-year-old won his 50th Test cap when Wales were beaten by New Zealand last weekend.
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.
Ospreys' Samoa international centre Kieron Fonotia, meanwhile, will head in the opposite direction next term when he links up with the Scarlets.