Marquinhos will leave AS Roma to join French champions Paris Saint-Germain.
The 19-year old Brazilian centre-back was the subject of bids from Manchester United and Barcelona but has opted for PSG who have signed him for around £30.1million.
"Thanks to all of you, the fans, the club, my team-mates. Go Roma, go forever and always," he wrote on Twitter.
"I will never forget what I've experienced at Roma. It was a joy for me and I will always carry you in my heart."