The France global penned a fresh five-year extension on Thursday, keeping him at the club until 2024, having previously turned down fresh terms.
Martial said he was delighted to renew his contract and was overwhelmed by the support of the United faithful.
Mourinho was eventually sacked due to his toxicity and regressive brand of football, and United legend Ole Gunnar Solskjaer was brought in as caretaker manager. That's one of the things I keep telling him - you've got to read and sniff whenever there is going to be a chance. He seems to be getting better and better as time goes on.
After embarking on a nine-match unbeaten streak under the Norwegian, Martial has chose to pledge his long-term future to the club, in a major boost for the team ahead of a crucial period of fixtures. We have players like him and Marcus Rashford, they score worldie goals.
Martial, who is expected to recover from a minor training injury to play at Leicester in the EPL on Sunday, has scored 10 goals this season, although he had gone more than a month without one before striking in the 3-1 FA Cup win at Arsenal on Jan 25.
Speaking about the deal, former Manchester United midfield maestro Paul Scholes couldn't contain his delight that Martial will be staying at the club until 2024.
Of the new contract, Solskjær said: "It's a confirmation that we are happy with him, we believe in him".
"I've been here for 15 years - coach, player, now manager - and I know how much this club can give to your career and what you can give to the club".
Anthony Martial has returned to the Manchester United squad after missing the midweek draw against Burnley through injury. I made my career and it was easy to sell the club to Anthony, but he knows what we're capable of.
However, according to The Sun, Solskjaer will be handed the full-time job if he manages to lead the team past PSG, with the first leg of their knockout-round tie due to take place at Old Trafford on February 12. "Anthony will do some rehab work but I would imagine he will be involved".
"We've not had a proper session since the game - hopefully both of them can get through that", Solskjaer said. He's had some ups and downs at the club - he's been top scorer, he's been developing.