Wade previously scored 82 tries in seven seasons with Wasps before joining the Buffalo Bills as part of the NFL’s International Player Pathway in 2019.
He scored a 65-yard touchdown on his debut for the Bills during pre-season, but never made a regular-season appearance.
He returned to rugby union in 2022 with a move to Racing, before linking up with Gloucester last summer.
Wigan legend Martin Offiah, who himself left rugby union to join Widnes in 1987, said Wade’s signing was big for the sport.
“Wigan’s signing of Christian Wade is the biggest coup for the sport of rugby league since Jonathan Davies joined me at Widnes back in the 80s,” he said.
Wigan head coach Matty Peet told the club website: “As well as working hard to learn a new sport, we are expecting Christian to bring his own personality to the team in terms of his athleticism, skill and experience.”
