It was officially announced through the club's website. Gallacher will join the Merseyside team's development squad who are currently top of the U23 league.
The youngster completed his move after training at Melwood for the whole of last week, where he had reportedly impressed staff with his ability.
Liverpool faced stiff competition from fellow Premier League club Swansea City, who were considered the frontrunners for the Scot's signature. However, he eventually opted for Jurgen Klopp's side because of their long-term vision.
The 18-year-old, who was a product of Falkirk's academy before stepping up to their first team, made 17 appearances this season in the Scottish second division.
January 27, 2018