Ashley Young’s first Premier League goal for 18 months, courtesy of a big deflection, saw Manchester United edge battling Brighton and Hove Albion at Old Trafford.
Brighton had been the better team up until Young’s attempt from the edge of the area hit Lewis Dunk before looping over keeper Mat Ryan and into the net.
Earlier, Anthony Knockaert and Pascal Gross both went close after getting behind the United defence.
Ryan produced a double save to keep out Romelu Lukaku’s header and Paul Pogba’s follow-up on the stroke of half-time.
United’s win cuts Manchester City’s lead at the top of the Premier League table to five points ahead of their trip to Huddersfield on Sunday.
Jose Mourinho offered Brighton boss Chris Hughton a hug at the final whistle – the United manager clearly relieved to have won a match despite a far from vintage display.
It required a huge slice of luck to finally breach the Seagulls defence in a scrappy game – Young’s deflected finish his first league goal since May 2016.
United are now unbeaten at Old Trafford in 39 league and cup games – their last home defeat coming against Manchester City on 10 September 2016.
City are the next Premier League visitors to Old Trafford on 10 December and Mourinho knows his side will have to produce a better performance than this to beat their title rivals.
Lukaku looked flat throughout and now has one goal in his past nine games while Paul Pogba was unable to have as much influence as he enjoyed the previous week against Newcastle.
This will go down as an ugly win but Mourinho and his players will not care if they are top of the table come next May.