The Brazilian joins from Palmeiras, in a deal that could rise to up to £31m.
It is understood that Manchester City beat Spanish giants Barcelona to the player's signature. Gabriel Jesus himself spoke of his delight at the move, and cited Pep Guardiola as one of the main reasons he joined the club.
"Manchester City is one of the best clubs in the world so I’m really pleased to sign. We have many great talents in the team and a fantastic manager in Pep Guardiola that I can learn so much from. I’m looking forward to showing the City fans what I can do and I think we’ll have a great future together," he told the club's official webiste.
The 19-year-old played 39 games for former side Palmeiras, scoring an impressive 19 goals. The forward is also a Brazil U-23 international but is yet to play for the Brazil senior national team.