Martin O'Neill has left Nottingham Forest just five months after being appointed as manager by the Sky Bet Championship club.
The 67-year-old - who made 371 appearances for Forest as a player, winning two European Cups - returned to the City Ground as boss in January.
The former Republic of Ireland manager guided the club to a ninth-placed finish in the Championship last term, but his short-lived tenure is now over.
A statement on the club's website read: "Nottingham Forest can confirm that manager Martin O'Neill has left the club.
"The club would like to thank Martin for all his efforts during his time at The City Ground and wish him well for the future."
O'Neill's assistant Roy Keane left the club on Sunday and reports have suggested player unrest is behind the former Celtic boss' departure.
The Northern Irishman took charge with Forest in ninth place but he failed to guide the club into the play-offs.
Forest have not played in the top flight since 1999 and will be on the lookout for their 12th manager since June 2011.
Forest then announced the appointment of Sabri Lamouchi as O'Neill's replacement.
The former France midfielder guided Rennes from the relegation places in Ligue 1 to qualify for the Europa League in the 2017-18 season but was sacked in December.
The 47-year-old - whose playing career took him to the likes of Monaco, Parma, Inter Milan and Marseille - also managed Ivory Coast at the 2014 World Cup.
"Nottingham Forest are delighted to announce that Sabri Lamouchi has been appointed as the club's new head coach," a statement on the club's website read.