Mourinho has been out of work since he was sacked by Chelsea in December.
With United failing to qualify for the Champions League under Louis van Gaal, the Old Trafford hierarchy are thought to have decided a change is required.
It is understood a deal with Mourinho was agreed in principle before Saturday’s FA Cup final victory against Crystal Palace.
The club plan to announce his arrival early next week after telling Van Gaal his reign has come to an end.
The Dutchman still has one season remaining on his three-year deal, but despite spending £250m on new players, his tenure has disappointed many fans, the club finishing fourth and then fifth in the Premier League.
Van Gaal’s grip on his job has seemed increasingly fragile this season, with Mourinho known to covet the task of masterminding a revival at United three years after legendary former manager Sir Alex Ferguson stepped down.
More to follow.
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