Tom Dele Bashiru has been signed by Watford on a six-year deal from Manchester City, Watford announced in an official statement.
His joining of Watford on a free transfer follows the expiration of his contract with Manchester City.
The 19-year-old is a central midfielder and made his senior debut in the EFL Cup in December 2017.
He is the Hornets' second first-team signing of the summer after defender Craig Dawson from West Bromwich Albion.
The Nigeria Under-20 international has played regularly at Premier League 2 level and will hope to make his Premier League debut when Watford host Brighton & Hove Albion on 10 August.