Ruben Amorim takes the reins as Manchester United coach

Manchester United have hired Ruben Amorim, gambling on a manager unproven in Europe's top leagues to turn around the fortunes of the fading English power.

At age 39, Amorim, who has joined from Portuguese champions Sporting Lisbon, will be the youngest United manager since the 1960s and the sixth permanent manager since the retirement of serial winner Alex Ferguson in 2013.

Amorim will take charge on Nov. 11, after completing his commitments to Sporting, and has signed a contract until June 2027, with United having an option of an additional year.

"Ruben is one of the most exciting and highly rated young coaches in European football," United declared on Friday.

The record 20-time English champions haven't won the Premier League since Ferguson's final season in charge.

Amorim's task will be to revive the glories of a club that has fallen way behind the best in England and Europe ? something which has proved beyond the likes of Louis van Gaal, Jose Mourinho and most recently Erik ten Hag, who was fired on Monday.

United are 14th in the 20-team Premier League, having lost four of their first nine games.

Amorim, a former Portugal midfielder who spent the majority of his club career at Benfica, joins after United paid 10 million euros ($A17 million) to release him from his contract at Sporting, which he led to two Portuguese titles in four full seasons in charge.

He has only worked in Portugal and has no experience of managing some of the game's top players under the constant glare of the world's media.

"He comes from a big club in Portugal," United defender Diogo Dalot told British broadcaster Sky Sports, "but I always say it almost quadruples the amount of intensity, the amount of pressure (at United)."

Amorim ended Sporting's 19-year title drought in the Portuguese league in 2021 to end the dominance of rivals Benfica and Porto, and won the League Cup that year, too, in his first season in charge.

Sporting also won the league last season and have won all nine of their league games in this campaign, bolstering Amorim's status as a burgeoning coaching prospect. In his only other top-flight role, at Braga, he won the League Cup in a stint lasting less than a season.

Amorim will finish his time at Sporting with a game against Estrela da Amadora on Friday, at home to Manchester City in the Champions League on Tuesday and with a trip to Braga on November 10.

In the meantime, Ruud van Nistelrooy will stay in control of United, taking charge of three games before the international break.

Amorim's first game with United will be away to Ipswich on Nov. 24.

He is taking charge of one of the world's most storied clubs, who have been in decline for the past decade and are in a period of upheaval following the arrival of a new soccer-focused leadership team fronted by British billionaire Jim Ratcliffe.

Ratcliffe will hope he has signed the latest coaching gem, with Amorim the youngest United manager since a 31-year-old Wilf McGuinness took charge in 1969.

The Premier League now has four managers in their 30s, with Amorim joining Brighton's Fabian Hurzeler (31), Ipswich's Kieran McKenna (38) and Southampton's Russell Martin (38).