The former Scotland international centre, 33 next week, registered 3700 points in a 16-year career, which saw him play for Rochdale, Whitehaven, Widnes, Oldham and Leigh, as well as Swinton.
“It was an extremely difficult decision for me to make and one that I thought long and hard about,” Nanyn said.
“But, once I realised that my body couldn’t do what my head wanted it to, I knew it was the right time for me to end my playing career.”
Swinton head coach John Duffy respects the decision made by the iconic player, and confirmed that the Lions would be offering Nanyn a coaching role.
“We are gutted to be losing Mick’s services but he has expressed his views for retiring on personal grounds which we totally respect,” he said.
“We have decided to offer Mick a role on our staff due to his qualities as a person and his outstanding knowledge of the game and we hope he accepts.”