The 27-year-old Grand Final winner has scored 200 points for the Saints since he signed from Hull FC in 2012.
He has made 107 appearances in a multitude of positions including centre, stand-off and loose forward.
Saints CEO Mike Rush said: “We’d like to thank Jordan for his commitment and effort in the red vee since he joined the Saints.
“His professionalism is second to none and we’re sure he will want to finish his Saints career on a high this year.”
Turner joined Hull FC from Salford City Reds in 2010 and won a Grand Final and League Leaders’ Shield with the Saints in 2014.
He will link up with his former Saints teammate Sia Soliola at the Raiders and fellow Englishmen Josh Hodgson and Elliot Whitehead.