Thompson makes the move back to England after a three-season and 32-game stint with the Canterbury Bulldogs.
While he started with promise during 2020 at the blue and white, the club was unable to pick up wins, and injuries for Thompson haven't helped in recent times - he played only four games in the most recent NRL season.
The forward managed to win two Super League Grand Finals overseas with St Helens in 2014 and 2019 and will be eager to repeat the effort with the Warriors. He has also managed seven appearances for England, which included being a member of the Lions Rugby Lague World Cup squad.
The confirmation of the move also means that the Dragons, Wests Tigers and Sydney Roosters have all missed out on his services after being linked to him in recent times.