The club made their announcement shortly after 1.30pm on Monday, with Everton chairman Bill Kenwright and CEO Robert Elstone having earlier arrived at the club’s Finch Farm training ground.
U23 coach David Unsworth has been placed in temporary charge of the team who travel to Chelsea in the Carabao Cup on Wednesday, before heading to Leicester in the Premier League as part of Sky Sports’ Super Sunday.
Everton spent heavily in the summer on players like Michael Keane, Davy Klaassen, Jordan Pickford, Gylfi Sigurdsson and Wayne Rooney but now lie 18th in the table having made their third worst start to a Premier League campaign.
The loss at Goodison Park on Sunday was Everton’s fifth consecutive match without a victory, with the Toffees having won just two league games this season, while they are also bottom of their Europa League group after two defeats and a draw in their first three matches.
Koeman said before the Arsenal game that Everton’s owners had faith in him to turn his side’s poor form around. However, the club’s hierarchy have clearly had a change of heart and released a statement on Monday announcing that the Dutchman had left his position.
“Everton Football Club can confirm that Ronald Koeman has left the club,” a statement on Twitter said.
“Chairman Bill Kenwright, the board of directors and major shareholder Farhad Moshiri would all like to express their gratitude to Ronald for the service he has given to the club over the past 16 months and for guiding the club to seventh place in last season’s Premier League campaign.”
Asked after the 5-2 defeat if he felt the result would cost him his job, Koeman said: “I don’t know.
“I told the players I believe in them. But if you are negative thinking – and everybody is doing that in this moment – all these kinds of decisions are not in my hands.
“That is normal because that is football. We have played nine Premier League games, against the first five of the Premier League last season, but this is not the position that is good for Everton.
“I understand that. I have worked a long time in football. First of all, I don’t think it is too late.”
After the weekend loss, defender Keane, who joined the club from Burnley in the summer, said the Everton players had let Koeman down and insisted they had to shoulder a great deal of responsibility for the side’s poor early season results.
“I think it is down to us at the end of the day, the manager can only do so much,” he told evertontv. “We have 100 per cent belief in the manager – we have done all season – and we hope we can get this right for him.
“We feel like we have let him down as a bunch of players and we are working hard to sort it out. It is not happening at the minute so we have to try different things to sort it out quickly.”