The 19-year-old centre-back joins City from Palmeiras, having made his senior debut in June 2024.
His performances in Brazil were outstanding, earning him a place in the prestigious Trofeu Mesa Redonda Team of the Year, which recognises the best players across Brazilian football.
"We've had Vitor Reis come from Palmeiras straight to the first team here. To have the opportunity to play for a big team like City with very good players around," said Fernandinho, according to the club's official website.
"I'm sure that his experience here will help him learn and he will be a different player in the future."
Reis becomes the latest Brazilian to represent Manchester City, following in the footsteps of stars like Gabriel Jesus, Fernando, and Elano.
He will also join compatriots Ederson and Savinho in Pep Guardiola's squad.
Manchester City have made significant strides in securing Juventus' versatile full-back Andrea Cambiaso, with agreements in place from the January transfer window set to be revisited this summer.
New Manchester City signing Nico Gonzales has expressed his delight at joining the club from Portuguese giants Porto on deadline day.
Premier League clubs spent a total of 370 million pounds in the latest transfer window, marking a significant increase from last year's 100m expenditure.
Manchester City's Bernardo Silva has opened up about the void left by former teammate Julian Alvarez's departure to Atletico Madrid in the summer.
