Former Chelsea midfielder Slavisa Jokanovic has replaced Billy McKinlay as Watford boss, only eight days after the Scot was put in charge.
The 46-year-old won back-to-back Serbian titles as Partizan Belgrade manager and joins the Hornets from Spanish third division side Hercules.
He becomes the Championship club's fourth head coach in 37 days.
Ex-Scotland international McKinlay did the job for only two games after Oscar Garcia's departure for health reasons.
Garcia had succeeded Beppe Sannino, who quit on 31 August amid growing tensions between himself and the players.
Watford are third in the Championship, level on points with the top two, and 45-year-old McKinlay was unbeaten in his brief spell in charge - a win over Brentford and Saturday's draw against Brighton.
Reports had emerged on Monday that McKinlay was expected to leave Vicarage Road and, explaining the decision to replace the former Blackburn midfielder so soon, Watford owner Gino Pozzo said the move was in the "long-term interests" of the club.
"There can be no compromise on this - whatever the circumstances," he said.
"I fully support and endorse the view from our technical staff that, given the talented squad which has been assembled and our position in the league, an experienced head coach with a winning pedigree is of primary importance to help ensure the success we are all striving for.
|Watford's managerial timeline|
|31 August - Beppe Sannino quits amid reports of an unhappy squad|
|2 September - Oscar Garcia appointed head coach|
|29 September - Garcia quits for health reasons, Billy McKinlay appointed|
|7 October - McKinlay replaced by Slavisa Jokanovic|
|See the full managerial ins and outs for September and October|
"The supporters of Watford have always been very understanding towards our project here and I am certain they will continue to do everything they can to support the new coach and his squad."
Jokanovic was a Yugoslavia and then Serbia & Montenegro international midfielder and was signed by Claudio Ranieri for Chelsea from Deportivo in 2000.
He played 53 games in two seasons at Stamford Bridge and retired shortly after, going on to become Partizan boss in 2007.
Between 2007 and 2009 he led Partizan to two consecutive league and cup doubles, and he went on to win the Thai title with Muangthong United in 2012.
Jokanovic speaks fluent Spanish, so would be able to work with Garcia's assistant coaching duo of Ruben Martinez and Javier Pereira, should the pair remain at the club.