The axe came despite Postecoglou guiding Spurs to a 1-0 victory in the Europa League final over fellow EPL side Manchester United in Bilbao last month.
It meant he had delivered on his promise of "always" winning a trophy in his second season.
But it also came at the end of a dismal EPL campaign in which the club finished in 17th place, just above the relegated trio.
Tottenham confirmed the sacking in a statement on Friday which read: "Following a review of performances and after significant reflection, the Club can announce Ange Postecoglou has been relieved of his duties."
Europa League success - Tottenham's first trophy in 17 years - brought an outpouring of emotion from Spurs fans and initially seemed sufficient to save his job.
Postecoglou even delivered a mic-drop moment during a euphoric open-top bus parade in front of an estimated 220,000 people when he declared "season three is better than season two", but chairman Daniel Levy had other ideas and appears to have dismissed the man to deliver him a much-craved trophy.
He had divided opinion among supporters during his two-year tenure and his job prospects had seemed bleak before winning the Europa League, European football's second-tier competition behind the Champions League.
Brentford boss Thomas Frank has been installed as the bookmakers' favourite to replace Postecoglou.
It all started so brightly for Postecoglou, with a run of eight wins from his first 10 league fixtures - despite the high-profile departure of Harry Kane.
That propelled Spurs to the summit but a sign of things to come was a thrilling loss to Chelsea in November, 2023 where several injuries occurred.
Fifth place in Postecoglou's debut campaign still represented an impressive finish but cracks started to emerge during an end-of-season 2-0 loss at home to Manchester City where some Tottenham fans were conflicted given a positive result would have put rivals Arsenal in the driving seat for the title.
Postecoglou later acknowledged that he misjudged the mood, but further run-ins would follow.
A slow start to the 2024-25 campaign was followed by Postecoglou's second-season trophy claim and a strong run of form as Spurs emphatically defeated Manchester United, Aston Villa and Manchester City.
But further injuries hampered progress and Spurs lost eight of their 11 EPL matches through a busy December and January programme.
The Carabao Cup provided some relief with a run to the semi-finals, but that ended in a 4-0 drubbing at Liverpool, while the slump in league form continued.
That left the Europa League, which Postecoglou delivered to the enraptured supporters.
But it was not enough to save him.
With PA
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