The Wales and British & Irish Lions full-back is the Blue and Blacks’ third signing in preparation for next season and follows in the footsteps of Thomas Young and Taulupe Faletau.
Williams replaces fellow Wales international Hallam Amos, who retires in the summer, and Cardiff director of rugby Dai Young is delighted to continue strengthening his squad with first class talent.
Young said: “We are all really excited to have signed Liam and look forward to welcoming him to Cardiff next season.
“We knew we had an opening at full-back and Liam’s talent and consistency is abundant for all to see. He has been one of the best full-backs in the world for a number of years and brings real quality on both sides of the ball with his attacking ability, kicking game, positioning and bravery.
“He adds further strength and experience to our squad and will not only strengthen us on the pitch but will be a key role model and leader for some of the young talent coming through in the back three.
“It is important that we have strength and depth across the board and we will continue to add quality to our squad when available.”
Williams came through the system at Waunarlwydd RFC before making a breakthrough at Llanelli and the Scarlets, where he has made 115 appearances during two stints, most recently in the New Year’s Day victory over the Ospreys.
The 30-year-old also starred during a two-year spell at Saracens, in which he scored 21 tries in 31 appearances and was integral in the English club’s 2018-19 Premiership and European titles.
He has been equally important on the international stage, scoring 16 tries in 72 Tests for Wales, where he has featured in two Rugby World Cups and won a Six Nations Grand Slam, while he has twice toured with the Lions, earning five Test caps.
Williams is now excited to embark on a new chapter in his illustrious career and hopes the move to Cardiff will ensure he remains at the top of his game for years to come.
He said: “I’m really excited to link up with Cardiff in the summer but remain very grateful to the Scarlets, who have given me so many opportunities in the game, and I’m fully committed to them for the rest of the season.
“I have lots of fond memories there but, at this stage of my career, I feel I need a change of scenery and environment to ensure I can stay at the top of my game.
“Cardiff have really impressed me recently and it feels like they are building something special. I have a lot of good friends there from the Wales squad and they cannot talk highly enough of the environment and Dai Young has convinced me that Cardiff is the best place for me to further my career.
“They have an enormous amount of talent in the squad, complimented by some really exciting young players, and the competition for places will be fierce but I am looking forward to playing my part and I am excited to see what we can achieve.”
