Roy Hodgson has stepped down as Crystal Palace boss so the club can “bring forward their plans to appoint a new manager”.
Hodgson, 76, was “taken ill” during training on Thursday amid reports he was to be sacked.
The Eagles have lost 10 of their past 16 Premier League games and are 16th in the table, five points above the relegation zone.
“This club is very special and means so much to me,” said Hodgson.
Palace visit Everton, who are 18th in the Premier League, on Monday night, with Hodgson’s assistants Paddy McCarthy and Ray Lewington in charge of the team.
Former Eintracht Frankfurt boss Oliver Glasner, 49, is the strong favourite to replace Hodgson on a permanent basis.
“I have fully enjoyed my time here across six seasons, as it has given me the chance to work with top-class players and staff doing what I love every day,” added Hodgson.
“However, I understand, given recent circumstances, it may be prudent at this time for the club to plan ahead, and therefore I have taken the decision to step aside so that the club can bring forward their plans for a new manager, as intended for this summer.
“I am confident that the season will finish well and I wish the team every success in the weeks, months and seasons to come.”
The club said Hodgson was now out of hospital and “doing well”.
“Roy has a special place in Crystal Palace history and this will never be forgotten,” said chairman Steve Parish.
“After four years in which he led the club to maintaining Premier League status season after season, he once again joined us nearly a year ago to steady the ship, and worked wonders. Quite simply, we owe our continued Premier League status to Roy.
“I would like to thank Roy enormously for his service and wish him the very best for the future; it’s fair to say Roy has the keys to Selhurst Park and will always be welcomed back.”
Hodgson was in his second stint in charge of Palace, having returned for the final 10 games of last season when he signed a short-term deal to take over from Patrick Vieira.
He led the club to 11th in the table before agreeing to continue to manage the side for the 2023-24 campaign, which Parish said “speaks volumes about his commitment to our club”.
His decision to take off midfielder Eberechi Eze in the second half of Palace’s FA Cup replay defeat by Everton, plus his handling of injured winger Michael Olise against Brighton, both drew strong criticism.
Olise limped off just 11 minutes after coming on as a half-time substitute at the Amex Stadium earlier this month.
Supporters have also displayed banners protesting at how the club is being run during recent games against Arsenal and Brighton.
Following the 4-1 loss to Roberto de Zerbi’s side, Hodgson said he had the “strength and resilience” to turn the team’s poor form around.
Glasner, 49, lifted the Europa League with Frankfurt in 2022 during his first season in charge when they beat Scottish side Rangers on penalties in the final.
After guiding Frankfurt to the knockout stages of the Champions League last year, the Austrian left the club at the end of the season with a year still left on his contract, following a 10-match winless run in the Bundesliga.