Hull will continue the search for their next manager after Mike Phelan left the club late on Tuesday night, with former Birmingham manager Gary Rowett the favourite to land the post.
The 54-year-old lost his job, which only became permanent in October, with the Tigers deep in relegation trouble, having picked up just 13 points from 20 games this season.
The Yorkshire club have already began looking for Phelan's successor and bookmakers have made Rowett the early favourite ahead of Alan Pardew, Wales' Chris Coleman, former England boss Roy Hodgson, Harry Redknapp and Ryan Giggs.
A Hull statement on Tuesday read: "The club can announce this evening that it has parted company with head coach Mike Phelan.
"We would like to thank Mike for his efforts both as assistant manager and head coach over the last two years.
"The search for a replacement has begun and an announcement will be made in due course."
The club did not say whether Phelan was sacked or resigned.
Former Manchester United midfielder Phelan stepped in after previous manager Steve Bruce left shortly before the start of the season. Bruce had only months earlier led Hull into the top flight.
The Tigers won their first two league matches of the campaign, against last year's champions Leicester and Swansea, but have been unable to build on that strong start. Their last win came on 6 November against Southampton.
They sit three points behind 17th-placed Crystal Palace, the last safe team, but have a far inferior goal difference to the Eagles and cannot afford to let points drain away as they did under Phelan, who was hampered by meagre resources.
Their next game comes in the FA Cup third round on Saturday against Swansea.
