Current under-18s coach Darren Fletcher, a former United midfielder and technical director between 2021 and 2024, will take charge of the team against struggling Burnley on Wednesday.
The BBC said the club were planning to appoint a caretaker boss for the rest of the season.
Names in the frame for the fulltime job include Enzo Maresca, who left Chelsea last week, Crystal Palace boss Oliver Glasner and former England manager Gareth Southgate.
Rising tensions
Amorim had hinted at deep frustrations on Friday, suggesting he was not being fully backed in the transfer market.
And he made a string of eye-catching comments after Sunday’s draw at Elland Rd, where he stressed he was United’s manager rather than “just the coach”.
The Portuguese told the scouting department and Wilcox “to do their job” during a blockbuster end to a post-match press conference that raised major doubts over his future.
And he repeatedly suggested to the media that he would leave when his contract expired in 18 months’ time.
But reports on Monday said United’s decision to axe their manager was because of the lack of progress rather than a power struggle.
The dismissal is a dismal end for Amorim, who won just 25 of his 63 games at United in all competitions during the shortest reign for a permanent manager since David Moyes was sacked just eight months into his tenure in 2014.
He had the worst win ratio (32%), the worst goals-conceded-per-game ratio (1.53) and the lowest clean-sheet ratio (15%) of any United boss in the Premier League.
Amorim arrived at Old Trafford to replace Erik ten Hag in November 2024 as one of the most sought-after coaches in world football following a successful stint at Sporting Lisbon, where he won two league titles.
But he was powerless to stop United’s slide to a 15th-place finish in the Premier League – their worst campaign for 51 years – at one stage describing his team as “maybe the worst” in the history of the club.
Amorim had the chance to end the 2024/25 campaign on a high in Bilbao but United lost the Europa League final against Tottenham and missed out on European football this season as a result.
The club backed their manager in the summer transfer window, spending more than £200 million ($467m) on new signings, including Bryan Mbeumo, Benjamin Sesko and Matheus Cunha.
But they have again flattered to deceive, winning just eight of their 20 league games so far and falling 17 points behind leaders Arsenal.
Amorim has been hit by injuries and a number of players are on Africa Cup of Nations duty but he has been criticised for sticking rigidly to his preferred 3-4-3 formation despite evidence it was not the best fit for his players.
His exit leaves the club searching for their seventh permanent manager since the retirement of Alex Ferguson, who left as a Premier League champion in 2013.
Since then, apart from the occasional cup success, the 20-time English champions have been also-rans, overshadowed by bitter rivals Manchester City and Liverpool.
-Agence France-Presse
