Josh Jones will join Exeter Chiefs for the 2016 Aviva Rugby Union Premiership season.
He has signed a two-year contract.
The 22-year-old made his debut for Saints against Warrington in March 2012 and has gone on to make 91 appearances for the Champions.
Originally from Chorley, he joined the club when he was 13 from Blackbrook but previously played for Leyland Warriors, Chorley Panthers and Union side Preston Grasshoppers.
He was England 15 and 16s captain and toured Australia with Saints Academy in 2009.
“It’s a new challenge for me and my family, but it’s one that we’re all really looking forward to,” he said. “Exeter are a great club, they’ve just come off the back of a fantastic season, and having watched them a few times on the TV, I like the style of rugby they play and the way they go about things.
“Hopefully I can go down there, add a bit to the squad using my experience from playing Super League and look to make my mark as quickly as possible.
“Obviously it’s a big change for me, I’ve been with the Saints since I was 13, but I think it’s a good move.
“I’m focused on seeing out what I hope will be another great year with St Helens. They have always been a big part of my life just because I’ve been there for so long.
“I’ve had some unbelievable times with the club, especially last season winning the Grand Final.
“That was pretty special, especially as we faced a fair bit of adversity along the way, but that in itself brought us all together and made us a lot stronger.”