Roberto Martinez has left Everton in the wake of Wednesday night's 3-0 defeat at Sunderland, the club have confirmed.
The 42-year-old, who replaced David Moyes as manager in 2013, had faced mounting calls for his departure after a run of just one win in their last 10 games.
And Everton announced on their official Twitter feed: "Everton Football Club regrets to announce that Roberto Martinez has left his position as First Team Manager with immediate effect."
The statement continued on the club's official website: "The chairman and the board of directors would like to place on record their thanks for the dedication and commitment Roberto has shown during his three seasons with the club.
"Roberto has been a great ambassador for the club, conducting himself, at all times, with the utmost integrity and dignity. He secured the club its highest ever Premier League points total, a place in the last 16 of the Europa League and appearances in both domestic cup semi-finals.
"He has also played a key role in the development of several young players, managing their progression to the Everton first team and international honours."
However, Martinez had faced mounting criticism over his tactics during the current campaign, as well as the form of big-name stars such as Romelu Lukaku, Ross Barkley and John Stones.
And the defeat at the Stadium of Light, which also guaranteed Sunderland's top-flight safety, effectively rendered Martinez's position untenable.
The timing of the impending departure will inevitably fuel speculation over a move for Frank de Boer, who announced he was leaving his role as Ajax coach on Thursday morning.
Outgoing Manchester City boss Manuel Pellegrini and former boss David Moyes have also already been installed among the favourites to succeed Martinez at Goodison Park. Amid mounting discontent, Martinez saw his side crumble 3-1 at champions Leicester last Saturday before Wednesday night's equally miserable performance against Sam Allardyce's men.
Fans had been planning to protest at the club's scheduled Player of the Year dinner in Liverpool last night.
Sam Allardyce, whose Sunderland side appear to have delivered the fatal blow to Martinez, said: "My sympathy goes out to Roberto, but he will no doubt bounce back."