Gerard Deulofeu is set to join Watford from Barcelona for an initial €13million (£11.5m) fee, the LaLiga champions have confirmed.
The 24-year-old has signed a five-year contract with the Premier League club, where he spent the second half of the 2017-18 season on loan.
The deal could cost Watford up to €17m (£15m) including variables, while Barca will receive a percentage of any future transfer fee.
"We are very pleased to welcome Gerard back to Vicarage Road and thank FC Barcelona for their part in concluding this deal," Watford chairman and CEO Scott Duxbury said.
"Our ambition to succeed and grow in the Premier League remains as strong as ever."
Deulofeu made seven appearances for Watford last season and scored a goal on his home debut in the 4-1 win over Chelsea in February.
The Spain international rejoined Barca from Everton last June, after he impressed during a loan spell with AC Milan.
The winger struggled for playing time under Ernesto Valverde, though, making only five starts in LaLiga before heading back to England with Watford.