The vastly-experienced 29-year-old won five caps for the Kangaroos in 2011 – including all four games in that year’s Four Nations – and has played more than 200 matches in the NRL for Cronulla and Wests.
Galloway – who has also played once for New South Wales in State of Origin – broke the news of his departure to team-mates following Wests’ clash with Sydney Roosters today and says he can’t wait to get started in Super League.
“I am really excited to be coming to the Rhinos,” Galloway said.
“I can’t wait to get over there and play for Leeds. It is a different style of competition, but I have watched it on TV and the chance to go over there and play in Super League is something that excites me.
“I am pretty close with Pat Richards and he’s obviously off to Catalans next season. He loved his time in England and when I mentioned to him that I was thinking about heading to the Super League competition he told me I would love it.
“When people like that tell you how good it is you take those comments on board.”
Galloway added: “One of the reasons I was sold on the Rhinos was the chance to be part of a team that is competing for silverware.
“I have never tasted success at senior level and hopefully I can achieve that at Leeds. I know the team are going really well and I am looking forward to watching the boys for the remainder of the season so I can familiarise myself with everyone’s names and get to know how the team plays before I get over here.
“I have always had a desire to come and play in the UK in my career and I have had the opportunity to stay in Leeds on a number of occasions when I have been over.
“It is a great city and I am looking forward to making it my home and being part of the English lifestyle.”
Galloway has Scottish parents and will not be included on the overseas quota.
Rhinos coach Brian McDermott said: “It is very pleasing to have reached agreement with Keith to bring him to the Rhinos.
“He is a highly experienced forward who will add to the group we already have in place for next season with the likes of Adam Cuthbertson, Mitch Garbutt and Brad Singleton.
“He is a no-nonsense front-rower who will take the team forward. Importantly, when you speak to anyone about him as a person, they cannot speak highly enough of him
“Having played for Australia and New South Wales, he is a significant signing for us and I am looking forward to the end of the year when he joins up with us.”
Rhinos chief executive Gary Hetherington added: “We are delighted to have attracted a player of the quality and experience of Keith to the Rhinos.
“I would like to thank Wests Tigers for how they have handled the matter with us and we look forward to welcoming Keith into the Rhinos family ahead of 2016.”
Rhinos close their First Utility Super League regular season campaign on Sunday at home to Catalans Dragons.