He will add to Chris Chester’s creative options for 2019 adding strength with Jacob Miller and Ryan Hampshire also in the half-back positions.
With Trinity still keen on Huddersfield Giants’ Danny Brough, goal-kicker Reynolds could also be used at full-back if needed next season.
“It is great to get this deal over the line,” admitted Chester.
“Ben is a fantastic young player who will bring a lot of energy to the squad alongside adding some depth and a bit of healthy competition to the halves.”
The Pontefract-born player started out his career at Castleford Tigers making a handful of appearances for them before spending most of 2014 on dual-registration with York City Knights where he won Championship One Young Player of the Year.
He moved to Leigh in 2015 and has made 65 appearances for the club, including playing in Super League last year.
Reynolds, 24, will link up with the rest of the squad for pre-season next month.
He added: “I am over the moon to be able to sign for a big club that is so close to home and also doing very well right now.
“It is a massive challenge ahead for me, firstly trying to work my way in to the team and then trying to help the team onto even bigger things in the future.”