Christened Richarlison de Andrade, the 20-year-old former America Mineiro attacker joins new signings Tom Cleverley, Will Hughes, Daniel Bachmann, Kiko Femenia, Harvey Bradbury, Sam Howes and Nathaniel Chalobah at the ambitious Premier League side.
Richarlison has signed a five-year deal for a reported £11m with the Hornets who are reforming ahead of the new season under Marco Silva.
Part of a statement from the club read: “The Hornets have beaten off strong competition to secure the services of the highly-rated 20-year-old, following a successful work permit application.
“A pacey and exciting forward with an eye for goal, Brazil Under-20 international Richarlison joins from Fluminense, where he played 67 games and scored 19 times.
“He came through the ranks at America Mineiro and has scored three times in 10 games for Brazil Under-20s.”
Chelsea and Manchester United were two other Premier League club’s also vying for the young Brazilian’s signature.