Leeds manager Jesse Marsch has been sacked after less than a year in charge.
Leeds lost 1-0 at Nottingham Forest on Sunday, their seventh Premier League game without a win.
They are 17th in the table - above the relegation zone only on goal difference - and last won in the league on 5 November.
Leeds finished 17th last season after American Marsch succeeded Marcelo Bielsa in February.
A club statement read: "We would like to thank Jesse and his backroom staff for their efforts and wish them well for the future.
"The process of appointing a new head coach is under way and we will continue to keep supporters up to date throughout the coming days."
Coaches Rene Maric, Cameron Toshack and Pierre Barrieu have also been sacked.
Leeds play Manchester United at Old Trafford on Wednesday and again at Elland Road on Sunday.
Marsch's side won only four of their 20 league matches this season, with six draws and 10 defeats.
Defeat by Nottingham Forest in his final match in charge left him with a 25% win-rate after 32 Premier League games as Leeds boss.
A former coach of RB Leipzig, New York Red Bulls and Red Bull Salzburg, he took over with Leeds 16th in the table.
They avoided relegation to the Championship thanks to a 2-1 win at Brentford on the final day of last season.
Jesse Marsch won less than 30% of his total games at Leeds United
Leeds have struggled again this season in the league, with their only top-flight success away from home this season coming at Anfield in October.
The win looked like it could be a catalyst for Marsch to build on and, after beating Bournemouth 4-3 at home a week later, Leeds moved up to 12th in the table.
But since then defeats by Tottenham, Manchester City, Aston Villa and Forest, plus draws with Newcastle, West Ham and Brentford, have left the club fearing relegation once again.
While their league form has been disappointing, Leeds have progressed to the fifth round of the FA Cup and will face either Fulham or Sunderland away at the end of the month.
Speaking after the Forest result, where his side had good chances in the first half to take the lead, Marsch said it was hard for him to accept the position the club finds itself in.
He added: "We are struggling to turn performances into results. We have been in this place for a while. It's frustrating.
"I've got to find ways to change that feeling and find ways to help our team to get the results we think we deserved."
Adam Pope, BBC Radio Leeds
It was a case of when not if for the axe to fall on Marsch, although the swiftness of the reaction by the board to Sunday's defeat at Nottingham Forest was unexpected.
The away support is always an accurate barometer of where a fanbase sits with regards its head coach and at the City Ground the calls for his head were so vociferous it felt even Marsch's most ardent backers were not prepared to spare him.
After a spectacularly successful spending spree in the January transfer market, including record signing Georginio Rutter, Max Wober and Weston McKennie, added to several significant incomings last summer the feeling is that Marsch was not capable of coaching an enviable squad to its potential.
The narrow Red Bull style he brought to Elland Road was a huge departure from the aesthetically pleasing one of his predecessor Marcelo Bielsa, and suffered constant criticism not least for an absence of consistent results as well as a confusing system.
Keeping Leeds in the Premier League in dramatic fashion last season after a brutal 12-game scramble for survival was one thing. But since then two wins and 11 points after beating Chelsea in August is the worst record of any Premier League side.
That brutal fact means Leeds are in a relegation battle and majority owner Andrea Radrizzani and shareholders San Francisco 49ers Enterprises, who are expected to complete a takeover, have both invested heavily and have acted decisively to protect their and the club's best interests.
It is likely that Chris Armas, who was appointed as Marsch's assistant just last week, will take caretaker charge of the trip to Manchester United. The club hopes to make a permanent appointment shortly.
The Bielsa widows may still weep but there will be few tears at the news of Marsch's departure. A really decent man but who was unable to coach Leeds United to the next level. The question is, who will?