The Wales outside half has been tracked by a number of clubs in recent weeks after stalling on a new deal at Stradey Park.
But Jones admitted it was a heart-wrenching decision to leave the Welsh region for pastures new.
"This club has been a very special place for me and it will be hard to leave," said Jones, who made more than 200 appearances for the Stradey Park outfit. "I come from Carmarthen and have always supported the Scarlets. I guess after this season I'll be a supporter again rather than a player!"
And Jones revealed he has no intentions of going out with a whimper and is desperate to help Gareth Jenkins' side clinch the Celtic League crown
"We've got two big games left and I'd love to be involved in both of them," he said. "I'd like to go out on a high with a Celtic League champions medal."
Stephen first played for the Scarlets - then Llanelli RFC - against Maesteg in 1996 and has made 207 appearances for the club/region, accumulating 1,908 points.
Scarlets Director of Rugby, Gareth Jenkins said: "Naturally we are disappointed that Stephen will be leaving us but we respect his decision and wish him every success at Montferrand. Stephen joined us at 18 years of age and has been a big part of what we have achieved over the last eight years. He is a terrific player, a dedicated professional and has many friends at Stradey. We all wish him well."