"He is a young player who did very well on loan at Dunfermline last season," said Southampton manager George Burley.
"He can play right or left and is a quick player who likes to take people on. He has bags of potential and I am very pleased to have got him.
"There was a lot of interest from other clubs so I am delighted the deal is done. We have had a couple of other players on loan from Liverpool recently and they have both come along very nicely during their time with us.
"Adam is coming to a club with good facilities and good young players and this is another step for him in his career."