As part of the release agreement, Wigan will have first refusal on Williams' services should he return to Super League once his time in the NRL has come to an end
Wigan executive director Kris Radlinksi said: "George has developed into one of the world's finest half-backs and, although we are naturally disappointed to lose a home-grown player of his calibre, we wish him the best in his move to the NRL.
"I have no doubt he'll take that competition by storm”
Williams, who has made 172 appearances for his home-town club, said: "Firstly I want to say a massive thanks to everyone at Wigan Warriors for everything they have done for me.
"I've been at Wigan since I was 12 years old and I have managed to live my dream playing 170-plus games and winning two Grand Finals for my home-town club, along the way making some incredible memories and friends for life
This was the statement when he left. After signing back JTomkins, Mossop, STomkins, Sarginson, JBurgess, Tommy, Bateman. I have faith we’ll get him back SHOULD he return to SL.