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.