The Frenchman will line up alongside Eugene Laverty next year as Aprilia look to defend the crown Max Biaggi won in 2012.
Guintoli made his debut on board the manufacturer's RSV-4 during testing at Jerez this week, but fans were made to wait before an official announcement was made as to the identity of the retired Biaggi's successor.
“Sylvain is a great addition to our team and we were very keen to have him. His excellent first contact with the RSV4 during the tests held at Jerez were also encouraging," Aprilia sporting director Gigi Dall'Igna.
"He proved to be a fast and solid rider straight away. He and Laverty will make a team to be reckoned with.
“We're preparing for the new season now. We have the world champion bike and two capable riders who always aim for top results, so I think we'll have fun.”
Guintoli said: "I am very happy, especially because the feeling with the RSV4 has been good right from the first few metres. To be able to sit in the saddle of the world champion bike is a great opportunity for me - one of the most important in my career.
“I think the bike has extremely high potential, as we've seen in the past few years, and I'm confident that I'll be able to put in some excellent results with it.”