Pichot, who was voted the Bristol Shoguns Supporters Club player of the year this season, has always said how much the Bristol club means to him as well as the supporters.
"The Club and the supporters have all made me and my family very welcome during our time in Bristol and I'm very sad to be leaving. I never thought that I would move on.
"There's a big challenge waiting at Stade Francais and there'll be a lot to live up to after their success this year, and I hope I can build up a similar relationship with the Stade Francais supporters that means as much to me as the people of Bristol do."
Pichot, who will be teaming up with international colleague Ignacio Corletto at the French giants, added: "The French club has some superb players and it'll be great to be competing in the Heineken Cup again."
After the Shoguns' relegation Pichot will be happy to have secured his future and concentrate on Argentina's World Cup campaign in the Autumn.
"I'd be lying if I said the last few months have been easy, but I can now leave knowing that there will be a Bristol rugby club in the city and the fans and supporters have something to follow.
"There is a huge amount of belief and commitment to rugby in Bristol and the supporters need to get behind the club in Division One. The atmosphere at our games last season was great and if it can be replicated in the new season, the Bristol club will stand head and shoulders above others."