The 26-year-old Llanelli Scarlets playmaker follows the day after Wales's record tryscorer Gareth Thomas announced he had joined European champions Toulouse from the Celtic Warriors.
Wales captain Colin Charvis is already in France having joined Second Division Tarbes prior to the World Cup last year.
Jones, who is out of contract with the Scarlets at the end of the season, had been linked with English giants Leicester but opted instead to sign a two-year deal with the French side. "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 and scored almost 2,000 points for the team.
"I am excited about moving to France, learning a new language and experiencing a different culture," said the 40-times capped Jones, who was leading scorer in the Six Nations tournament with 55 points.
Scarlets director of rugby Gareth Jenkins said there was no hard feelings despite Jones' decision to quit. "Naturally we are disappointed that Stephen will be leaving us, but we respect his decision and wish him every success at Montferrand," Jenkins said.
"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."
Jones could still go out on a high note by winning the Celtic League with Llanelli and is in danger of joining a side that risks being in the French Second Division next season despite having players of the calibre of French internationals Olivier Magne, Aurelien Rougerie and New Zealand-born Tony Marsh.
Montferrand, who are in the European Challenge Cup final, made Jones their priority to replace former French international fly-half Gerald Merceron. The Scarlets will replace Jones from within by handing Gareth Bowen the fly-half role full time.
Jenkins admitted Welsh clubs were unable to compete financially with the French sides and with Wales having performed well in both the World Cup and the Six Nations the players were bound to attract attention. "There are players within my squad who have been offered huge amounts of money to play in England and France," Jenkins said.
"That's a big concern because we cannot match them. We do not have the money - it's as simple as that."
New Wales coach Mike Ruddock said that he wanted in an ideal world all the best players to remain in the country, so they could help strengthen the domestic game by encouraging sponsors and increased crowds. "My principle is that we want to keep all our best players within the Welsh regions if possible," he said.
"We want to be as as strong as we can so we have more chance of winning the European Cup with a Welsh region.And we want the fans to see our best players playing in Wales and we want those guys to help us achieve greater attendances and better sponsorship. So it is a blow when we lose players."
AFP - 2004.
