And Davies, who has been ruled out of action for up to five months due to a pectoral injury, has paid tribute to the west Wales region.
"Deciding to leave the Scarlets has been the toughest decision of I've ever made; it's certainly not one I've taken lightly and took some time to think over looking ahead in my career and the exciting opportunities available to me now," said the British & Irish Lions centre.
"The club did its very best to find a way for me to continue at Parc y Scarlets and I'm proud to have been part of a region that has such a strong rugby heritage and stands out in the way it invests in local talent.
"Some of the best times I've had in my career so far have been in a Scarlets shirt in Europe and my most memorable game for the region will always be London Irish away when the travelling support was amazing.
"I'm looking forward to when I get back from injury and doing all I can to make sure the Scarlets finish this season on a high.
"There's a real drive and ambition from everyone at Scarlets players and coaches to compete at the top of the league and Europe; they're working hard to strengthen the balance of the squad and the desire and expectation to really compete going forward are high.
"Playing for the Scarlets and being part of the West Wales rugby community has been a huge part of my life.
"It's seems almost unreal when I've reflect on what's happened over the past three years and what I've been part of from the World Cup to Six Nations and then the Lions.
"I'm really grateful for the opportunities I've had so far in my career and it's important to me that I say publicly how much I really appreciate the efforts of the people who have shown faith and handed those chances to me.
"That foundation and the values you gain from rugby at an early age stay with you wherever you go and play in the world and this is now a fresh new opportunity to widen my experience in France.
"Growing up in Carmarthenshire you are aware from an early age of what Welsh rugby means in this part of the world and being selected for the Scarlets for the first time was a proud day.
"They'll be a whole group of new Scarlets getting their opportunities right now in our region during the LV=Cup and the kick and ambition that gives you as a young player is great - to know who's worn that Scarlets jersey before and what they have achieved."