LD Sports has not yet officially launched, but will be a sports content, marketing and entertainment platform in China.
Its logo will appear on the front of the first-team jerseys through to the end of the 2021-22 campaign.
Southampton did not reveal the deal value however.
But the club said the partnership would also see LD Sports’ logo on the front of the Under-23s’ and Under-18s’ shirts, along with the various squads’ training kit.
The deal is part of Southampton’s attempt to broaden their appeal in China under the ownership of Jisheng Gao.
David Thomas, the club’s commercial director, said in a statement: “It’s an exciting challenge.
“We are looking forward to using our growing credentials and awareness in China, as well as our content and digital marketing expertise, to help the brand achieve its business objectives over the next three years.”
Southampton finished 16th in the English Premier League (EPL) this season with 39 points from 38 matches.