Neil Lennon has confirmed he has left Celtic after four years as manager following talks about his future.
It is understood that the former club captain had been considering his position for some time despite winning the Scottish title for the third time.
"I have parted company with Celtic," the 42-year-old Northern Irishman said in a brief statement.
"The club are in a very strong position and I wish the fans and the club all the very best for the future."
Lennon has often expressed his desire to eventually manage in the Premier League in England.
Speculation had grown this summer about Lennon's position after his assistant, Johan Mjallby, confirmed he was leaving to "seek some different opportunities".
Lennon's representative, though, said that the Northern Irishman had "nothing lined up" at another club.
"Four years is a good spell to be manager of a club like Celtic, but now Neil wants to look ahead to the next chapter of his career," said Reilly.
"He just feels now is the time to move on to the next challenge."
A former midfielder who started his senior career with Glenavon in his homeland, Lennon played for Manchester City, Crewe Alexandra and Leicester City before joining Celtic in 2000.
He had a seven-year spell as a player at Celtic Park, and returned as first-team coach in 2008 after short spells with Nottingham Forest and Wycombe Wanderers before taking charge in 2010 after a spell as caretaker.