Paris Saint-Germain completed their estimated €32 million capture of Marquinhos on Friday to take their spending this week past the €100 million mark.
Following the arrivals of Edinson Cavani from Napoli and Lucas Digne from Lille for an estimated €77 million combined, PSG announced on Friday evening they had scooped up the highly-rated Brazilian defender, 19, from Roma on a five-year deal.
"The arrival of Marquinhos, a great player in the making whose qualities have attracted Europe's biggest clubs, is a source of real satisfaction for Paris Saint-Germain," club president Nasser Al Khelaifi said in a statement on PSG's official website. "It shows our will to look ahead to build one of the biggest teams in Europe."
The centre-back, who will wear the No. 5 shirt, only played 26 Serie A games in the Italian capital after joining the Giallorossi from Corinthians a year ago.
"I'm very happy to be able to join Paris Saint-Germain, which has seen many Brazilian players mark its history," said the teenager, whose arrival to play alongside compatriot Thiago Silva could force France international Mamadou Sakho to leave PSG this summer.
"I'm going to do all I can to continue that tradition, and take my turn to write some great pages of the club's history. Paris Saint-Germain is going to allow me to improve alongside some exceptional players with the hope of winning trophies and the hearts of the supporters."
French media reported earlier on Friday that, while undergoing a medical on the outskirts of Paris, the Brazilian had been found to have "some anomalies on the body" according to the doctor who was examining him, throwing the move into doubt.