The 37-year-old former England skipper has signed a five-month deal and announced he would be donating his salary to charity.
"I'm excited, it's something we've been working on and talking about for quite a while," he said.
"I've a lot of experience. I've won trophies throughout my career and played with the biggest and best clubs."
The former Manchester United midfielder added: "One of the reasons I wanted to come to Paris was we decided on something quite unique throughout my time here.
"I won't receive any salary. My salary will go to a local children's charity. That's one of the things we are excited and proud to do. It's something exciting and I'm not sure it's been done before."