Ghisolfi has been named new director of football at the Black Cats after leaving AS Roma at the end of last season.
The Frenchman said, "The Club, the players, the staff and the fans achieved an extraordinary result last season.
"Together, these people brought Sunderland back to the Premier League, and I am determined to bring my experience to support this group and ensure the team is ready to take the next step."
Ghisolfi addeds: "This is an exciting challenge and I look forward to working alongside Kyril, Kristjaan and Régis as we embark on this exciting new chapter in Sunderland's history with our fans."
Exciting new chapter
Sunderland owner Kyril Louis-Dreyfus, 27, also said: "We have had an incredible journey over the past four years and now we face a new challenge as we prepare for life in the Premier League.
"Florent's appointment marks an exciting new chapter in that journey.
"This appointment strengthens our capabilities in line with the Club's long-term vision, and evolving our management structure in this way reflects our ongoing commitment to building a sustainable and competitive football club.
"I am confident that the players, staff and supporters will join me in welcoming Florent to Sunderland and supporting him in his new role."