The Red Devils continued their fine form, leaving it late to cap off 3 wins in a row with another clean sheet, even after a heroic performance from Kasper Schmeichel in goal tried to salvage something for the Foxes.
Leicester's rock-solid defensive finally gave way in the 70th minute as Mourinho's men quickly dispatched off the visitors, courtesy of the 3 substitutes who all contributed to the scoreline.
Marcus Rashford and Marouane Fellaini came off the bench to get on the score-sheet, as Jesse Lingard also appeared to notch up an assist to cement Manchester United at top of the league.
Here are the player ratings:
Manchester United
David De Gea - 7.5/10
The Spaniard had a relatively untroubled first half and dealt with the defensive distribution with ease. However, he was called to action at the turn of clock and maintained composure to contain a resurgent Leicester attack. Bagged his third clean sheet in a row.
Antonio Valencia - 6.5/10
The captain for the third game in row showed his usual levelheadedness in defence but seemed slightly off the mark while going forward. His crosses were wayward and he couldn't do enough break down a resilient opposition side, who often frustrated his forward forays.
Eric Bailly - 8/10
Eric Bailly proved yet again why he is an early contender for the best defender of the season. He was superb in coming into tackles and did a fantastic job keeping Vardy in a tight pocket throughout the game.
Phil Jones - 7.5/10
Jones had another commendable game and had a ball of a time in marking Okazaki out of the game. His forays in attack were a strangely welcome sight. Though he was intimated by Mahrez in the second half on a few occasions, he did a fine job.
Daley Blind - 6.5/10
Blind had an above average game playing in an unchanged defensive setup. Even though he made brilliant readings of Pogba's long passes and put in a couple of quite decent crosses, his contribution in attack was generally wasteful. He had some troubles with the resurgent Leicester attack in the second half and was just barely able to deal with it. More effort needed from the Dutchman.
Nemanja Matic - 8/10
On a day like today when United's attacks were slow in progression, Matic remained his usual best. His forward passing was as crisp and accurate as ever, and his spacial awareness allowed him to break down Leicester's attacks with ease. A revolution in midfield.
Paul Pogba - 7.5/10
One of the powerhouses in the first half, Pogba dominated the game with his pin-point long passing, starting off attacks at whim. Though he had a staggering 6 long shots in nearly 20 minutes in the first half, they often left the Frenchman frustrated as a couple of them just about missed testing Schmeichel's goal. Even then, he never diminished in creativity, as his performance only improved in second half.
Juan Mata - 7/10
Mata had a decent game and was unlucky to not get a goal, as his rebound was ruled offside. Later on, his shot brought out a great save from the keeper. The Spaniard continued to keep the attack flowing but his presence diminished greatly as the game went on.
Henrikh Mkhitaryan - 7/10
The Armenian tried to link up with his attacking partners in the usual manner, but was largely frustrated by a solid visitor's defence. Even though he got booked early on in the second half, he delivered when it mattered, notching up another assist from a corner. Another day at work for the league's top assist-maker.
Anthony Martial - 8/10
Starting his first league match of the season, Martial was at the heart of all United's attacks in the first half, as he often dropped deep. His movement was unmatchable and created some brilliant chances. Even though his efforts didn't bear any tangible fruits, his performance was met by warm applause from the stadium's faithful.
Romelu Lukaku - 6/10
Lukaku had a tough game. He was heckled by the opposition centre-backs for the most part and wasn't able to get the better of them. He ended up wasting some decent chances, including a weak penalty.
Substitutes
Marcus Rashford - 8/10
Rashford had an immediate impact after his substitution, scoring a goal in less than 3 minutes after coming on. His direct running created a lot of panic in the Leicester half.
Marouane Fellaini - 8/10
Fellaini created an almost superb chance with his first touch to release Lukaku on goal. He maintained his super-sub performance, getting his name on the score-sheet.
Jesse Lingard - 7.5/10
Like his fellow subs, Lingard delivered almost immediately after coming on the field, notching up an assist for Fellaini's goal. His usual hardwork helped see out the game with ease.
Leicester City
Kasper Schmeichel - 7.5/10
Schmeichel made a brilliant save early on to deny Juan Mata's curler and made an even more sensational save from the penalty spot to deny Lukaku. Despite an unreal performance, the big Dane was unlucky to concede the two late goals, as Leicester crumbled late in the game.
Christian Fuchs - 6/10
Fuchs had solid time defending on right flank in the first half and didn't let crosses come in. However, he was always on the back foot due to a continuous United attack and couldn't do much, as his side conceded the late goals.
Harry Maguire - 7/10
Harry Maguire justified his England call-up with a riveting performance. His clearances were on point and he barely conceded any innocuous fouls. Largely kept Lukaku quiet during the entire game, only once ever conceding a free-kick in dangerous position. One of Leicester's best player on the day.
Wes Morgan - 6.5/10
The Captain on the visitor's side put in a decent shift with his well timed blocks and maintaining a defence under constant threat. In spite of that, he should've done better to check Rashford for the first goal.
Danny Simpson - 6/10
Simpson was troubled by Blind and Martial throughout the game. He ended up conceding a handball from a Martial shot but was let off easy after the save. Largely remained a weak point in a tight defensive setup.
Marc Albrighton - 5.5/10
With his side on back foot, Albrighton didn't do a very good job of stopping the opposition's midfield pressure. His presence was largely unnoticeable apart from a a few crosses and he got subbed off at the hour mark.
Matthew James - 6.5/10
One of the better midfielders on the visitor's side. James tried to start Leicester's attacks with his first time passes and tried his best to contain United's attacks in the first half. Later on, he got into the book for a clumsy challenge on Rashford.
Onyinye Ndidi - 5.5/10
Ndidi seemed overwhelmed for most of the game, clearly not able to contain the midfield battle. Even though he had a few important clearances in and around the box, he didn't stick to Rashford in the box for the first goal. A largely forgetful performance from the midfielder.
Riyad Mahrez - 7/10
Mahrez couldn't get into his creative freedom and barely did anything in the first half. However, after the restart, he spearheaded the resurgent Leicester attacks, with a dangerous low cross. He showed some flashes of his title-winning form, but those were far and few in between.
Shingi Okazaki - 6/10
Okazaki had a steady duel with Matic and Jones and largely uninvolved throughout the game due to that. He couldn't link up with Vardy and was substituted without an effect at the half hour mark.
Jamie Vardy - 6.5/10
The Englishman was often left isolated. His tackling was good but he barely had enough chances to get out of his own half to continue the buildup of the Leicester attacks.
Substitutes
Demarai Gray - 6.5/10
Brought on much needed energy with his pace to trouble the defenders but could barely get into the game to cause any damage. His decision making was questionable, as he wasted easy passes.
Andy King - 5.5/10
King barely had an effect on the game as United's attacks never ceased. He remained largely invisible as his side finally crumbled to the home side's attacks.
Islam Slimani - 5.5/10
Came on too late and could barely affect the outcome.