In a short post on Twitter, the club wrote: 'City are delighted to announce the signing of Brazilian midfielder Douglas Luiz #WelcomeDouglas'.
He is the second Brazilian to join Manchester City in less than a year after the arrival of striker Gabriel Jesus from Palmeiras in January.
However, it's understood that he will be loaned out to Spanish side Girona for the 2017-18 season, although neither club has confirmed that move, and City say they will make a statement on his future "in the coming days".
Turkey to extend state of emergency for 3 months
Ankara blames the followers of US-based Turkish cleric Fethullah Gulen for the attempt to overthrow the government. The bridge has been officially renamed the July 15 Martyr's Bridge following the dramatic events on that date.
Game of Thrones Deaths Most Likely to Happen in Season 7
Martin recently gave us a hint about the toll that being resurrected has taken on Beric - which could be bad news for Jon too. The whole thing costs $50 and takes 45 minutes, and comes with a mimosa of rosé bubbly and - you guessed it - dragon fruit.
Turkey dismisses 7400 civil servants in latest anti-coup purge
The government has blamed the coup attempt on loyalists of Fethullah Gulen, a Turkish cleric who lives in exile in Pennsylvania. The government has since purged more than 142,000 people from the civil service and the military using emergency decrees.