Forest confirmed the Australian's dismissal in a brief statement on social media, saying:
"Nottingham Forest Football Club can confirm that after a series of disappointing results and performances, Ange Postecoglou has been relieved of his duties as head coach with immediate effect. The Club will make no further comment at this time."
Postecoglou's appointment on 9 September came after Forest parted ways with Nuno EspÃrito Santo amid tensions with owner Evangelos Marinakis. Marinakis had identified Postecoglou as his top target, but the move has quickly unravelled, leaving Forest in the Premier League relegation zone and still searching for their first win under his leadership.
The 60-year-old's brief tenure has entered the record books as the shortest managerial reign in Premier League history, surpassing Les Reed's 41-day spell at Charlton Athletic in 2006. Postecoglou managed only five league matches, one more than Frank de Boer's ill-fated stint at Crystal Palace in 2017.
His reign began with a 3-0 defeat at Arsenal and quickly descended into frustration. Forest blew a 2-0 half-time lead to lose 3-2 at Swansea in the Carabao Cup, drew 1-1 at Burnley, and conceded a stoppage-time equaliser to Real Betis in a 2-2 Europa League draw.
The side then suffered four consecutive defeats, against Sunderland, Midtjylland, Newcastle, and Chelsea, with fans turning against him after the Europa League loss to the Danish champions.
Postecoglou, sacked by Tottenham in June, had insisted only last week that Forest were improving under his guidance. "I get that it's part of the fanfare of the Premier League that it needs one manager to be in the spotlight," he said after the Newcastle loss.
"If people want to assess me three and a half weeks into the job, there's nothing I can say or do that will change that. But what I have seen and felt in this period is that we are heading in the direction I want us to. The results will come."
They never did. With Forest preparing for crucial fixtures against Brentford and West Ham, the club are now searching for their third permanent manager since December 2023.