The 31-year-old, who has made 23 appearances for Wales, has admitted his delight after agreeing terms with the club.
"This is a fantastic opportunity for me and one I am really looking forward to. I have always thought that a move to rugby league could be an option for me at some point in my career and when I learned of Wigan Warriors interest I was excited about the chance to make the switch," Powell told reporters at a press conference.
"Wigan Warriors are the biggest name in rugby league; they also have a rich history of Welsh connections over the years and are a huge name in the Principality.
"I am thrilled to be given this chance and with the help of the Wigan Warriors coaching staff, I am looking forward to being able to make the transition between codes. This is a huge new chapter in my rugby career and I can't wait to get started."
Powell will link up with the club in May.