Leicester City have sacked manager Craig Shakespeare just four months after he signed a three-year deal to take the job on a permanent basis.
The Foxes are third from bottom in the Premier League and have not won any of their past six league matches.
Shakespeare, 53, succeeded title winner Claudio Ranieri in February, initially on a temporary basis.
Michael Appleton will take caretaker charge of the squad, who were not told in advance of Shakespeare's sacking.
Their next game is against Swansea City in the Premier League on Saturday.
- Analysis: 'A sacking that should surprise no-one - least of all Shakespeare'
- 'Leicester sacked Shakespeare too soon' - Schwarzer
In a BBC Sport poll, 71% of voters thought it was wrong to sack Craig Shakespeare.
Shakespeare won eight of his 16 games in charge last season, and led the club to the Champions League quarter-finals.
After steering the Foxes away from trouble to finish in 12th place, he was given the job permanently in June.
His departure follows a 1-1 draw with West Brom on Monday.
The last time Leicester went six league matches without a victory, Ranieri was sacked - nine months after leading them to the title.
Of their 10 matches this season - eight in the league and two in the EFL Cup - Leicester have won three and drawn three, losing four.
But they have won only once in the league - a 2-0 victory at home to Brighton on 19 August.
Their four defeats have come against Arsenal, Manchester United, Chelsea and Liverpool.
Why the club decided he had to go
Leicester City vice-chairman Aiyawatt Srivaddhanaprabha
"Craig has been a great servant to Leicester City - during his spells as an assistant manager and since taking over as manager in challenging circumstances in February. His dedication to the club and to his work has been absolute and the contribution he made to the most successful period in Leicester City history is considerable.
"However, our early promise under Craig's management has not been consistently evident in the months since and the board feels that, regrettably, a change is necessary to keep the club moving forward - consistent with the long-term expectations of our supporters, board and owners.
"Craig is and will remain a very popular, respected figure at Leicester City and will be welcome back at King Power Stadium in future, both professionally and as a friend of the club.
"The club will now begin the process of identifying and appointing its next first-team manager and will make no further comment on the process until the appropriate time."
The West Brom curse?
Shakespeare - a former West Brom player - is the seventh manager in the past five years to leave his job in the aftermath of a match with the Baggies:
- Mick McCarthy was sacked as Wolves manager in 2012 after losing 5-1 at home to the Baggies.
- Andre Villas-Boas suffered the same fate at Chelsea after a 1-0 defeat at The Hawthorns in March 2012 and, eight months later, his successor Roberto di Matteo departed after a 2-1 defeat at the same ground in his final league match (his final game in charge was against Juventus in the Champions League).
- Roberto Mancini was sacked by Manchester City despite having just beaten West Brom 1-0 in May 2013.
- Paolo di Canio lost his job at Sunderland after losing 3-0 to the Baggies in September 2013.
- Chris Hughton was sacked by Norwich after losing 1-0 to WBA in April 2014.
- And Sir Alex Ferguson's final match in charge of Manchester United before retiring was also against the Baggies - a 5-5 draw in May 2013.
BBC Radio Leicester's Ian Stringer
Craig Shakespeare knew the ruthless nature of Premier League management when he took the job, but eight games will have been a surprise to him, I'm sure.
I chatted to him pre-season, when he said he was well aware of the difficulties of having Arsenal, Manchester United, Chelsea and Liverpool in the first six league games.
And having Danny Drinkwater sold on deadline day only to discover the paperwork for his replacement - Adrien Silva - was 14 seconds late left meant depleted numbers.
Shakespeare's association with the club goes back to Nigel Pearson's appointment in 2008, with a break when the pair managed Hull City, so it's a long-standing romance with European victories along the way. It ended against West Brom, a club he played for.
Fans' reactions seem mixed. Many remember the night against Sevilla when Shakespeare took charge and secured Leicester City a Champions League quarter-final place, while some claim that achievement and resulting appointment was a step too far for an inexperienced manager.
I'll miss him. Above all, he's a nice man. They're rare in football.
Who could replace him?
Carlo Ancelotti, recently sacked by Bayern Munich, former England manager Sam Allardyce, ex-Manchester United boss David Moyes and former Crystal Palace manager Alan Pardew all figure prominently in the betting markets.
Also among the potential candidates are former Oxford boss Appleton, who has been placed in temporary charge and had been working as Shakespeare's assistant, Wales manager Chris Coleman and ex-Man City boss Roberto Mancini.
Former Leicester striker James Scowcroft told BBC Radio 5 live he believes the club will go for "a big name".
"They will go totally different," he said.
"They went for a name in Claudio, a man who has managed at the highest level in Europe. It's a club that needs to go forward not backwards now. They need to reinvent themselves.
"I'm shocked and sad for Craig. It hasn't worked out and it's been a tough start. It's a results game and the performance last night wasn't good."
'It's ridiculous' - reaction
Former Leicester goalkeeper Mark Schwarzer on BBC Radio 5 live
I was surprised, I thought it was a bit too soon to sack him. You could see the response he got from the players last season.
Last night they did seem to lack a bit of that fighting spirit, and they were a bit lucky to get back in the game, but they've had a really tough start to the season and there have been signs that they are not far away.
Would Ancelotti be suitable for a club like Leicester? I am not sure. Allardyce is not always a fans' favourite but he has evolved, and his record in the Premier League is excellent.
It is a crucial decision. But if you get the biggest possible name, you are not necessarily getting the right person for the job.
Stoke midfielder Charlie Adam
I could not believe it.
These owners just think they can do what they want. I think it's ridiculous.
They are not a top-10 club. I know they won the league and have invested, but Leicester are in there with Stoke and West Ham, fighting in mid-table. They are not going to challenge for sixth place, they are a mid-table team.
Ex-England defender Danny Mills
You have to be realistic, the league title was a complete anomaly, something that is never going to happen again.
If they finish in the top 10 that should be a brilliant season by their standards. The owners, fans, everyone has got to understand that they can't compete with the top clubs, they are not at their level.
For me, the players have to take some responsibility - it is the same squad that won the league not so long ago.
Of those, the only player who has improved is N'Golo Kante, and he has moved on to Chelsea.
Your reaction on #bbcfootball/81111 on text
Matt Pell: Not all Shakey's fault. Recruitment has been shambolic. Champions to chumps.
Sean Bravery: Are the owners unaware of how Leicester have done over recent years, bar 'that' season? They are not a top-six team, not even a top-half one.
Dennis Ethan: Carlo Ancelotti to Leicester City?
Mark: I'm very surprised by the timing of Craig Shakespeare's sacking. The list of possible candidates is very poor, I'm tired of the likes of Alan Pardew being linked with our club.
Leicesterboy1: Champions to basement in less than two years! Should never have sacked Ranieri. Bring in Ancelotti and let's get moving.
Joseph: Not the first time a manager has been sacked at the expense of this overpaid and lazy Leicester team. Need to move on from the class of 15-16, otherwise this sacking streak will just continue.