Here, Press Association Sport looks at where the Portuguese coach might go next.
Mourinho is still a hugely-popular figure in Milan after he won an unprecedented treble with the Italian club in 2010. Current boss Luciano Spalletti is under pressure with his side out of the Champions League and a distant third in Serie A.
Another of Mourinho's former clubs, and one whose president Florentino Perez has reportedly considered hiring the Portuguese for a second spell at the club. Mourinho led Real to the LaLiga title in 2012 but left the following year after a fall-out with senior players.
Paris St Germain
Having won titles in Portugal, England, Spain and Italy, maybe France would be the next natural step for the 55-year-old. Mourinho would surely relish the chance to work with Neymar, Kylian Mbappe and Edinson Cavani. Plus they face United in the Champions League early next year.
With Mauricio Pochettino heavily linked with Manchester United, could a job swap prove viable? Mourinho enjoyed living in London during his stints with Chelsea and would inherit a squad seemingly far better equipped to challenge for honours than the one he has left behind.
Mourinho has said he prefers the day-to-day routine of managing a club but now could be the time to give international football a try with his native Portugal. Fernando Santos is the current boss and led Portugal to the Euro 2016 title.