The Nigeria striker has joined in a straight loan from Napoli with a break clause for January.
He said upon signing his contract: "When I heard about Galatasaray's interest, it was an easy decision for me. I knew how big Galatasaray was and how much of a family club it was. They have an incredible fan base.
"Henry Onyekuru is my friend and he played for Galatasaray, he told me how big the club, the fans and the people here are. So it was an easy decision for me. When I landed at the airport, the fans welcomed me with so much emotion that I felt very happy. These things are important for a player. I want to do everything I can for them. I can't wait to start this project. I'm very excited."
On a reunion with former Napoli teammate Dries Mertens, he continued: "Dries Mertens was always with me when I played in Italy. He became a big brother to me. He is a person I respect a lot, I am excited to be teammates with him again. I can't wait to meet my teammates as soon as possible. I was already watching Galatasaray games.
"I follow Mertens to see how he plays since he came here. I was following his development as a person and as a footballer. The interactions of the players with the fans when they score goals and win games are also exciting. Now I hope our fans will support me after every goal. I can't wait.
"I say hello to the Galatasaray fans, Osimhen is here. Thank you very much for welcoming me at the airport. It was a great welcome."
Gala have also announced that Osimhen will wear the No45 shirt this season.