USA international Thretton Palamo will join Bristol ahead of the club's 2016/17 Premiership campaign.
The bulldozing 107kg centre – who has fifteen caps for his country – arrives from Saracens.
Palamo spent last season on loan at London Welsh, making five appearances before a call-up to the USA Sevens team.
“Thretton is a big, physical player who has explosive power and pace,” said director of rugby Andy Robinson.
“Thretton is raw and has lots to learn, but we are confident he can flourish in our environment.
"We’ve seen in the past with the likes of David Lemi and Fautua Otto that there are players on the sevens circuit who can make a real impact in the fifteens game.”
Palamo represented the USA during the 2007 Rugby World Cup, becoming the youngest player in history to feature in the tournament at that time. He also featured against Japan at Kingsholm during the 2015 tournament.
He said: “It’s a fresh challenge at Bristol and another opportunity to prove myself in the top flight of English rugby.
“Hopefully I can bring some of the skills and experience I’ve taken from the Sevens circuit and contribute to the fast-flowing game that Andy [Robinson] wants to play.”