AFC Wimbledon manager Neal Ardley has left the club by mutual consent.
He was the third longest-serving boss in England's top four divisions, having taken over in October 2012.
The 46-year-old's assistant Neil Cox is also leaving, with first-team coach Simon Bassey named as interim manager.
The Dons are 23rd in League One with just three league victories all season, although they have won their past two matches in the FA Cup first round and Checkatrade Trophy.
Ardley led Wimbledon to promotion to League One for the first time since the club was formed in May 2002, when they beat Plymouth Argyle 2-0 in the 2016 play-off final at Wembley.
He was previously a stalwart with the old Wimbledon FC - making almost 250 appearances for the club in an 11-year spell from 1991 and helping them reach FA Cup and League Cup semi-finals in 1997.
"Neal has been a credit to the club in everything he has done," chief executive Erik Samuelson said in a statement.
"He is a clear thinker, a superb man-manager and a fine coach. I've enjoyed working with him and am absolutely certain that he will achieve even greater success in his next roles.
"He leaves with my personal thanks and gratitude for what he has done in his time here at AFC Wimbledon."
Wimbledon's poor form this season has ultimately cost Ardley his job.
A win on the opening day at Fleetwood Town was followed by five winless games in the league, including a run of three successive defeats.
Despite September starting with a 1-0 victory at Gillingham, they lost 10 of their next 11 games - with a 2-1 win over Oxford on 29 September preceding a seven-match losing streak.
That run finally ended with a 4-0 Checkatrade Trophy win over Stevenage and a last-minute 1-0 FA Cup victory at Haringey Borough, who are 18th in the seventh-tier Isthmian League Premier Division.
Only Morecambe's Jim Bentley and Wycombe's Gareth Ainsworth were the only two EFL managers to be in their positions longer than Ardley, although Ainsworth was in caretaker charge of Wanderers when Ardley was appointed by Wimbledon.
Rob Stevens, BBC Sport
AFC Wimbledon have struggled following an overhaul of the playing squad this summer, which saw 11 new signings arrive at Kingsmeadow and a host of long-serving players depart.
Ardley warned last week that he would be sacked if they were knocked out of the FA Cup in the first round. However, even a 1-0 victory over non-league Haringey Borough was not enough to keep him in a job.
Wimbledon fans will remember Ardley's crucial role in their history, saving the club from relegation from League Two on the final day of 2012-13 and then leading the club to promotion to the third tier in 2016 following a memorable play-off final victory.
The next appointment by the supporter-owned Dons will be key, as the phoenix club face up to the possibility of being relegated for the first time in their history.