Jose Mourinho's side extended their unbeaten run to 21 league games at a sun-drenched Stadium of Light.
Jose Mourinho's side extended their unbeaten run to 21 league games at a sun-drenched Stadium of Light, with Henrikh Mkhitaryan and substitute Marcus Rashford also on target.
United closed to within four points of fourth-place Manchester City, on whom they retain a game in hand, but will drop back to sixth if Arsenal win at Crystal Palace on Monday.
Sunderland, who had Seb Larsson contentiously sent off in the first half, now lie 10 points from safety at the foot of the table and look destined for the Championship.
Victory set United up nicely for Thursday's trip to Anderlecht in the quarter-finals of the Europa League, a competition which guarantees a Champions League place to the eventual winners.
Mourinho's men won with plenty to spare, enjoying 70 percent of possession and playing against 10 men for more than half the game.
Any hope Sunderland had of replying to Ibrahimovic's 18th league goal of the season on the half hour were all but ended when his former Sweden team-mate Larsson was sent off as the interval approached.
Larsson was shown a straight red card by referee Craig Pawson for leading with a raised foot in a challenge on Ander Herrera, sparking furious Sunderland protests.
With left-back Luke Shaw enjoying a rare United start as England manager Gareth Southgate looked on from the directors' box, Ibrahimovic broke the deadlock with a bolt from the blue.
The 35-year-old took a pass from Herrera on the edge of the Sunderland area, easily held off Billy Jones and fired a low shot into Jordan Pickford's bottom-left corner.
Pickford had already saved well from Jesse Lingard and only a brave block from Bryan Oviedo prevented Marouane Fellaini from stretching the visitors' lead following Herrera's inviting cut-back.
It proved to be Jones's last intervention before the Sunderland right-back was forced off by a hamstring problem.
Mkhitaryan had scored with a stunning 'scorpion kick' in the victory over Sunderland at Old Trafford on Boxing Day.
He got his name on the scoresheet again in more prosaic circumstances just 46 seconds after the restart.
From the kick-off, Sunderland failed to touch the ball as the Armenian was afforded time and space to send a low angled drive past Pickford from 15 yards to notch his ninth goal of the season.
Paul Pogba should have made it three, but produced a wayward volley from an Ibrahimovic flick, before the France midfielder aimed a long-range free-kick narrowly wide.
Rashford put a more realistic slant on the final score a minute from the end as Sunderland were stretched to breaking point by a swift counter-attack.
It ended with Rashford swapping passes with Ibrahimovic before finding the bottom-left corner with a confident finish.
Sunderland have lost five of their last six games and failed to score for the seventh consecutive game, a desperate run of over 11 hours.