The 33-year-old first moved to Llanelli in 2005 and made a massive impact over the next six years with his skill, vision and ball skills earning rave reviews during a 143-game stint with the Scarlets before joining Clermont Auvergne in 2011/12.
Scarlets Head Coach Simon Easterby said: “To have the quality and experience of a player like Regan King back in our squad next season will be a big positive for our region as a whole.
“Not only will we have secured a rugby player of real quality on the pitch who has played at the top end of European and French rugby for the past two years, but we’ve also gained the value of a professional who has such rounded experience which can be passed onto others.
“He’s shown his inherent quality as a player in his recent performances in the Heineken Cup as well as the domestic French game and is a player any club in Europe would want in their ranks.
“What Regan can bring will hopefully inspire our young backs further and the depth of experience and creativity he’s known for will have a positive impact throughout the squad. You only have to recall what a big influence he had on early senior careers of Jon (Davies), Rhys (Priestland), Gareth (Maule) and many others in his time with us to recognise that value.
“We’re delighted he’s returning to Parc y Scarlets, it will be a warm welcome back home for him and his family and we know as a group of coaches and players that he will help add a different dimension and edge to Scarlets Rugby next season.”
