The former Scotland U20 second-row and FOSROC Scottish Rugby Academy player joins from French Federale 1 side Stade Nicois and will link up with Glasgow Warriors ahead of the 2020/21 season.
Bain has spent two seasons with Stade Nicois as part of a performance partnership with Scottish Rugby. In his time with the French side, the 22-year-old made 37 appearances scoring three tries.
Born in Edinburgh, he also won ten caps for Scotland U20 and was part of the squad that finished fifth at the 2017 World Rugby U20 Championship - the highest-ever placing by a Scottish side.
Speaking to glasgowarriors.org, Bain said: "It's exciting to be coming back to Scotland and getting the chance to play rugby on home soil.
"I spoke to Danny (Wilson) and I've been really impressed with what he has to say about the club's culture and his vision for the Warriors.
"I can't wait to represent Glasgow. They're a really strong side and growing up watching Edinburgh and Glasgow it's kind of a dream come true to have the chance to be playing professional rugby for them. I'm honoured to be able to have the chance to compete for the jersey.
"I enjoyed my time at Stade Nicois and it has been really good for my game. They pride themselves on their physicality and scrummaging which has been great for development as a tight five player."
Bain becomes head coach Danny Wilson's fourth signing at second-row, joining fellow boiler house options including former European Player of the Season Leone Nakarawa, Scotland internationals Scott Cummings and Richie Gray and the recently re-signed Kiran McDonald.
Wilson said: "We're looking forward to welcoming Hamish into the squad. He is a big young athletic lock with good lineout defence and a rugby brain.
"He has come through the Scottish system and is spoken of in high regard by John Dalziel, who coached him at Scotland U20s.
"Stade Nicois play in a very physical league which will have no doubt helped his development and when joins us he will have the chance to continue that development and learn from world-class locks like Leone Nakarawa, Richie Gray and Scott Cummings."