Quique Sanchez Flores has been sacked by Watford, just 85 days after he was re-appointed for a second spell in charge of the Premier League club.
The Spaniard, who replaced countryman Javi Gracia after four games of the league season, won just one of his 10 Premier League matches.
Watford suffered their eighth league defeat in a 2-1 loss against fellow strugglers Southampton on Saturday, which saw them remain bottom of the table on eight points and six adrift of safety.
The decision was taken after Sanchez Flores met with chief executive and chairman Scott Duxbury along with owner Gino Pozzo on Sunday, with the appointment of a successor described as "imminent".
"Quique is a man of great integrity and it was clear how much he wanted to have a positive impact, but ultimately results have dictated our decision," said Duxbury in a club statement.
"The appointment of a new head coach is imminent, and with nearly two-thirds of the season remaining, we will provide all the support necessary to make the coming months successful."
Former Brighton and Newcastle manager Chris Hughton is a strong contender for the Watford job, with the club hopeful of appointing their new head coach in the next 24 hours, Sky Sports News understands
Ex-Derby and Swansea boss Paul Clement, who has been out of work since he was sacked by Reading last December, is also understood to be in the frame to replace Flores.
Watford moved off the bottom of the table with a 2-0 victory over Norwich on November 8, but the club have since suffered back-to-back defeats against Burnley and Southampton.
Aside from the win at Norwich last month, the only other victory during Sanchez Flores' brief 12-game tenure was against Swansea in the Carabao Cup.
Sanchez Flores was previously in charge at Watford between June 2015 and May 2016, during which he guided the club to an FA Cup semi-final.
The 54-year-old, who led Atletico Madrid to the Europa League title in 2010, is the third Premier League boss to be sacked since mid-November - after Tottenham and Arsenal dismissed Mauricio Pochettino and Unai Emery respectively.
Flores' heartfelt farewell to Watford fans
"I would love to say a big thank you from my heart for the appreciation, respect and support that I've felt in each moment I've lived in the lovely family that Watford FC is.
"This is not the time to think about individual feelings, it's time to have a collective reaction.
"Peacefully, for having taken the risk needed for someone and something I love: Watford FC and football.
"Hope, passion, fight, commitment, effort, hard work and luck.
"Drop by drop, until we achieve it. I wish you all the best. Stay strong! You'll always be in my heart."
Will Watford go with 'tried and tested' as successor?
Analysis from Sky Sports News' Paul Gilmour:
"Traditionally when they have brought in a new head coach it has been perhaps an unknown or somebody unexpected.
"Chris Hughton would slightly go away from that in that he is tried and tested. He has a very good record in the Premier League, certainly in terms of keeping sides up.
"With two-thirds of the season to go it is a big appointment for Watford."
Analysis from Sky Sports' Ron Walker:
"Although painfully out of form for much of 2019, this is still largely the same squad which did break that positional record and reach that cup final. But instead of rejuvenating the dressing room, his return to Vicarage Road just continued its decline.
"Sanchez Flores was the right man for Watford in their first season back in the top flight but two poor spells abroad before his return did not mark him out as the obvious successor to Gracia."
What's next for Watford?
Watford will travel to Leicester on Wednesday in the Premier League, before they host Crystal Palace at Vicarage Road on Saturday.