The player announced the news to Scarlets supporters on social media this morning ahead of the big Boxing Day derby against the Ospreys.
Having started his professional career with the Scarlets eight years ago, Williams has gone on to earn a reputation as one of the best all-round No.15s in world rugby.
Capped 62 times for Wales, where he has played wing and full-back, he started in all three Lions Tests during the drawn series in New Zealand in 2017.
During six seasons for the Scarlets, he scored 29 tries in 111 appearances, helping the side to the Guinness PRO12 title in 2016-17 before joining Saracens where he was an English Premiership and European Champions Cup winner.
As well as club success during a glittering 2019, Williams was a key member of Wales’ Six Nations Grand Slam-winning side and the squad that reached the semi-finals of the Rugby World Cup. In a list of the 100 best players in the world this year, Rugby World magazine named him fifth.
The 28-year-old will rejoin the Scarlets ahead of the 2020-21 season with his signing a clear indication of the ambition of the region.
“We are delighted that Liam is heading home to the Scarlets,” said general manager of rugby Jon Daniels.
“He is one of the leading players in world rugby and to be able to sign a player of his calibre at the peak of his powers highlights our determination to build a squad that will challenge for silverware. Having Liam playing alongside the likes of Leigh Halfpenny, Johnny McNicholl, Steff Evans and our exciting young back-three talent is a mouthwatering prospect.
“Liam came through the ranks here at Parc y Scarlets; he understands the culture and values we stand by and also what we want to achieve.
“He is an attacking runner that can light up games, while his ability in the air and defensive qualities are second to none. There is no doubt we are signing a world-class player.
“Liam is also a popular figure with players, coaches and supporters and we are all excited by the prospect of seeing him back here at Parc y Scarlets.”
Looking forward to returning to the Scarlets, Williams said: “I’ve thoroughly enjoyed my time at Saracens over the past three seasons. The environment has undoubtedly developed me as a player and a person. I am grateful for the support I’ve had from the players, management and supporters during this time. The opportunity to return home to the Scarlets was too good to turn down and I am incredibly excited about the future.”
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