Rankin, 21, is a former team-mate of scrum half Jacob Miller, and the pair are set to link up again at the KC Stadium in 2014.
He said: “It’s a big move from the Gold Coast but I’m looking forward to the opportunity and to the challenge of playing in the Super League.
“I spoke to the management and they were really keen to get me over there in the team and I’ve got a good mate in Jake playing over there too.
“It’s going to be a great opportunity for me to improve my own game and not many people know me over there in England, so it’s a chance for me to start afresh and play my own brand of footy.”
“To have signed a player of this quality is very exciting for us and despite a pretty detailed and lengthy recruitment focus on the half back position, he was the one player that always came out on top throughout the process.
“I was extremely impressed with his character and how level headed he was for a young man throughout the talks we had, whilst he has received some very positive feedback from Australia.”