The 25-year-old put pen-to-paper on Sunday as Nantes boss Claudio Ranieri looks to ensure he has a squad capable of building on last season’s seventh-place finish.
Girotto has spent the majority of his career in Brazil with the likes of Metropolitano, Hercilio Luz, Tombense, America Mineiro, Palmeiras and most recently Chapecoense, while he also enjoyed a spell in Japan with Kyoto Sanga.
The midfielder attended Saturday’s 1-0 Ligue 1 loss to Marseille and insists he is pleased to sign for such a big club.
Girotto told Nantes’ official website: "I am pleased to be here. Nantes are a big club. I also contacted several players in the French league who told me I was making the right decision.
"My first impressions are very good, looking at the infrastructure. It is a great honour to work with the coach."