Chelsea have sacked manager Graham Potter after less than seven months in charge following Saturday's 2-0 home defeat by Aston Villa.
It was the Englishman's 11th defeat in 31 games since replacing Thomas Tuchel at Stamford Bridge on 8 September.
Chelsea have dropped to 11th in the Premier League - 12 points outside the top four - having spent more than £550m on new players this season.
The club's owners said they were "disappointed" to sack Potter.
Chelsea say Potter "has agreed to collaborate with the club to facilitate a smooth transition" and that Bruno Saltor, who worked with Potter at Brighton, will take charge of the team as interim head coach.
In a statement, co-controlling owners Todd Boehly and Behdad Eghbali said: "We have the highest degree of respect for Graham as a coach and as a person.
"He has always conducted himself with professionalism and integrity and we are all disappointed in this outcome."
Chelsea host Liverpool in the Premier League on Tuesday and face Real Madrid in the first leg of their Champions League quarter-final on 12 April.
There have now been 13 managerial changes in the Premier League this season, with Leicester sacking Brendan Rodgers earlier on Sunday.
'Along with our incredible fans, we will all be getting behind Bruno and the team as we focus on the rest of the season," the Chelsea owners added.
"We have 10 Premier League games remaining and a Champions League quarter-final ahead. We will put every effort and commitment into every one of those games so that we can end the season on a high."
Former Spanish right-back Bruno, 42, spent seven years as a player at Brighton before retiring in 2019 and moving into coaching.
Potter was Boehly's first managerial appointment since taking over the club in May 2022, with the Englishman impressing in his three years at Brighton.
Potter replaced Tuchel, who won three trophies in 20 months at Stamford Bridge, in September when the Blues were sixth in the top flight, following a summer during which they spent £255m on transfers.
Owner Boehly went on another remarkable spending spree in January, shelling out £288m.
Argentina midfielder Enzo Fernandez and Ukraine forward Mykhailo Mudryk were among eight mid-season signings - but the new additions have struggled to click on the pitch.
Analysis - Lack of progress was Potter's downfall
BBC Sport's Alex Howell
Things have moved quickly at Stamford Bridge. On Sunday morning, the media plan was sent out for the press conference that Potter was due to be holding on Monday afternoon before the match against Liverpool, but by 8pm that evening he was no longer in charge.
The feeling at Stamford Bridge is that it was not solely the poor results that have led to his dismissal but a lack of progress from the team overall.
The decision to relieve him from his post was led by Paul Winstanley and Lawrence Stewart the co-sporting directors, with backing from chairman Todd Boehly and co-owner Behdad Eghbali.
It is understood that Potter will not receive the full five years payment for his contract that he signed in 2022.
It is felt that having Bruno in charge will give the team the best chance of salvaging the season.
The search for a new manager begins now but it is not expected that a replacement will be named in the next few days.
Chelsea abandon 'long-term approach' with Potter
Potter's dismissal is Chelsea's 17th managerial change this century and, of the full-time incumbents of the role, his reign was by far the shortest.
Only Luis Felipe Scolari (36), Andre-Villas Boas (40) and Roberto Di Matteo (42) failed to reach the 50-game mark and even interim manager Rafael Benitez (48) lasted longer than Potter.
Chelsea paid Brighton in excess of £21m in compensation for Potter to bring him to Stamford Bridge. Boehly said at the time that he fitted "our vision" and had "skills and capabilities that extend beyond the pitch which will make Chelsea a more successful club".
That indicated Chelsea were looking to pursue a long-term approach in the dugout after sacking Tuchel.
After a promising start of nine games unbeaten, including five successive victories and comfortable qualification for the knockout stages of the Champions League, things began to unravel just before the break for the World Cup.
The slide began with a 4-1 humbling at his former club Brighton, followed by defeats against Arsenal and Newcastle and a Carabao Cup exit at Manchester City.
They returned from the World Cup break with a 2-0 victory over Bournemouth, but won just three of their next 13 league matches.
Potter's side were also thumped 4-0 at Manchester City in the FA Cup third round in January, but overturned a first-leg deficit against Borussia Dortmund last month to reach the Champions League quarter-finals.
In February, Potter says his mental health suffered after he and his family received anonymous abuse following the club's poor run of form.
First sacking for manager with previous record of success
Until his brief reign at Chelsea, Potter had enjoyed managerial success at each of the three clubs he had served.
He led Swedish side Ostersunds from the fourth tier into the top flight with three promotions in five seasons and won the 2017 Swedish Cup, earning a spot in the Europa League and reaching the knockout stages of that competition.
In his one subsequent season with Swansea City in 2018-19, they finished 10th in the Championship following relegation from the top flight and reached the FA Cup quarter-finals where they led Manchester City 2-0 before losing 3-2.
Potter was then recruited by Brighton and, after three seasons of steady progress, led them to their highest-ever Premier League finish of ninth last term as well as collecting plenty of praise for their style of play.
They sat fourth in this season's table when he left for Chelsea in September.
Since his departure, Brighton have continued to thrive under new manager Roberto de Zerbi and are pushing for a European place.
