He is expected to arrive in Glasgow within the next few days.
Starting his sporting career playing college football in San Mateo, California, Langilangi first took up rugby for the East Palo Alto Razorbacks where he was a teammate of former Warrior Folau Niua.
Impressive performances earned him a PRO Rugby contract and his first cap for the USA Eagles against Russia in June.
Speaking exclusively to glasgowwarriors.org, Langilangi spoke of his excitement at joining Glasgow.
He said: "There was interest from other clubs, but joining Glasgow Warriors was an easy decision.
"I've heard a lot of positive things about the club and the city from Greg Peterson and I'm looking forward to getting over to Scotland to start training with the squad.
"I've watched a few GUINNESS PRO12 matches and I'm excited about the physicality and speed of the game.
"There are some great players who play in the backrow at Glasgow, so I'm going to have to work very hard to earn my place, but it's a challenge I'm looking forward to."
Glasgow Warriors head coach Gregor Townsend added: "We've been working on getting Langilangi here for some time and we were aware that there was a lot of interest in him from other clubs. So we're delighted that he's joined us and we're looking forward to integrating him into our squad as soon as possible.
"He is a strong ball carrier and hits very hard in the tackle. There will be a lot for him to work on and learn about how we play, but he will bring a high level of physicality to our forward pack, as well as increasing our strength in depth in the backrow."
Guinness PRO12 Warriors News
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