Chelsea have announced on their official website that Robert Kenedy has left the club to join Watford on a season-long loan deal.
He moved to Stamford Bridge during last summer's transfer window and played more than 20 games for the Blues, scoring two goals.
He can play as a left-back but also in midfield.
The 20-year-old was described as a versatile addition to Walter Mazzarri's squad on Watford's official website.
A statement on Chelsea's official website said: "Kenedy has today joined Watford on loan until the end of the season.
"The 20-year-old attacker moved to Chelsea from Fluminense in his native Brazil last August and made his debut in a home game against Crystal Palace.
"His goal away at Norwich in March, which came after just 39 seconds, was the fastest scored in the Premier League last season.
"Kenedy made 20 appearances in total for the Blues last season, and will gain further experience with the Hornets."