Neil Lennon has resigned as Celtic boss, the club has confirmed.
The club said the Lurgan man had resigned with immediate effect.
"We thank Neil sincerely for all he had done for the club and we wish him every success going forward," the club said on Wednesday morning.
Lennon's departure comes in the wake of the Ross County defeat on Sunday.
It has been a disastrous season for the Hoops with the club trailing rivals Rangers by 18 points.
The club started the campaign bidding to complete an unprecedented 10-in-a-row league championships.
Through the course of the season the misery was compounded by early exits from the Champions League, Europa League and even the Scottish League Cup, also at the hands of Ross County.
After that loss in November, Lennon has been under intense pressure.
I have worked as hard as ever to try and turn things around.Neil Lennon
Neil Lennon said: “We have experienced a difficult season due to so many factors and, of course, it is very frustrating and disappointing that we have not been able to hit the same heights as we did previously.
“I have worked as hard as ever to try and turn things around, but unfortunately we have not managed to get the kind of run going that we have needed.
"I have always given my best to the club and have been proud to deliver silverware to the Celtic supporters. The Club will always be part of me. I will always be a Celtic supporter myself and I will always want the best for Celtic.
“I would like to thank so many people at the club who have given me so much and I would also like to thank my family for their love and support. I wish the Celtic supporters, players, staff and directors nothing but success for the future.”
The club statement continued: "Neil has served the club with distinction as both player and manager, delivering numerous successes, most recently completing the domestic treble in December. In his second period as Celtic manager, he has achieved five trophy successes, to add to his three League titles and two Scottish Cup victories in his first period as manager.
Neil has always been and will always be a true Celtic man.
John Kennedy and Steve Clarke are the early favourites to become the next permanent Celtic manager, with Rafael Benitez, Eddie Howe and Roberto Martinez also among the bookies' frontrunners.
Celtic Chief Executive Peter Lawwell added: “I would like to pay tribute to Neil for all he has done for the club in his second spell, delivering our eighth and ninth successive league titles, the quadruple treble and winning the last five available domestic trophies.
“Neil has always been and will always be a true Celtic man and someone I will always hold in the highest regard.
“I have watched Neil fight many battles over many years, on and off the field, with a courage and tenacity few could match. Even this season, he has fought so hard and worked tirelessly to turn things around.
“While this season has not progressed as we would have liked, it cannot diminish the character or integrity of a man who has given the club so much.
“Personally, it is a sad day for me to see Neil leave the club. Neil is a man of quality and decency, he is someone who will always be part of the fabric of Celtic and someone who will always be welcomed at Celtic Park.
“On behalf of everyone at the club, and personally, I would like to thank Neil for his work as our manager and I wish him and his family good health and continued success in everything they do.”
Celtic’s principal shareholder Dermot Desmond added: “Neil is a Celtic legend both as a player and manager. He has given so much to the club, and with his success over the last number of years – including winning a Treble in his own right – he will be very difficult to replace.
“We thank Neil sincerely for all he has done for the club and we wish him every success going forward.”