Match ends, West Ham United 0, Manchester United 2.
Wayne Rooney scored two goals, including an exquisite lobbed finish, as Manchester United overcame Robin van Persie's absence to win at West Ham.
Rooney, now third in United's all-time goalscorers list on 212, put his side ahead with a stunning lob from just inside the Hammers' half.
The England striker doubled the lead after Mark Noble's attempted clearance fell straight to Rooney to steer home.
West Ham were poor, Andy Carroll's tame header the closest they came to a goal.
United manager David Moyes, without Netherlands striker van Persie for up to six weeks due to a sprained knee, has had little to smile about this season.
But Rooney's spectacular eighth minute finish had the Scot out of his seat in the dug-out applauding a truly wonderful goal.
There were shades of David Beckham's memorable finish from the halfway line for United against Wimbledon in 1996 as Rooney, spotting Adrian well off his line, outmuscled James Tomkins before unleashing a brilliant lob which sailed over the goalkeeper and into the net.
This was United's ninth Premier League win away from Old Trafford, where the Red Devils return on Tuesday for the Manchester derby.
While United's domestic home form - five defeats in 14 games - continues to frustrate Moyes, he is at least finding some solace on the road.
With Beckham and England manager Roy Hodgson in the Upton Park main stand, United carried on where they left off after reviving their Champions League campaign at Olympiakos' expense on Wednesday.
Rooney's spectacular finish set the tone for a comfortable victory to move back to within three points of fifth spot in the table.
The Hammers should have equalised in the 15th minute.
But Carroll, who was unmarked, spurned a glorious chance to give Hodgson a reminder of his goalscoring prowess ahead of the World Cup when he headed straight at David De Gea from close range.
United, who had Michael Carrick as a makeshift centre-back in the absence of the injured Rio Ferdinand and suspended Nemanja Vidic, carried a threat each time they went forward.
Shinji Kagawa, on only his eighth league start of the campaign, forced a fine save from Adrian before the Spaniard beat away a goal-bound shot from countryman Juan Mata.
But United, who also recalled Alexander Buttner, Marouane Fellaini, Darren Fletcher and Ashley Young, established a two-goal cushion in the 33rd minute.
Moments after the Hammers had claims for a penalty waved away when Noble went to ground under a Fletcher challenge, Young powered deep into West Ham's half.
His cross fell to Noble who could only kick the ball into Rooney's path and the United man made no mistake from close range.
West Ham still have to secure their Premier League survival and face Liverpool (home), Arsenal (away) and Manchester City (away) before the end of the season.
Sam Allardyce can only hope his team can raise their game after a limp performance.
The damage had already been done when Fellaini crashed to the ground inside the West Ham penalty area after Antonio Nocerino's challenge in the closing stages.
But there were few complaints from the visitors when referee Lee Mason waved away their appeals. United had the points safely in the bag.
West Ham United manager Sam Allardyce:
"The first goal knocked the stuffing out of us.
"It's such a wonderful goal, you've got to admire the finish, but to get off to a start like that when we were looking forward to this game, having won the last three at home and trying to get more points on the board.
"Straight away you're 1-0 down against a side that have got an abundance of talent.
"I definitely thought there was a foul [leading up to the first goal].
"When the ball comes forwards, James Tomkins is going to try and win it. Wayne, not making an attempt for the ball, pushes him with his left arm."
To see a photo gallery from all of Saturday's Premier League matches, go to BBC Sport's Facebook page.
- 19CollinsBooked at 33mins
- 14TaylorBooked at 39minsSubstituted forNocerinoat 83'minutes
- 21DiaméSubstituted forJarvisat 58'minutes
- 4NolanSubstituted forColeat 72'minutes
- 1de Gea
- 2da SilvaBooked at 11mins
- 8MataSubstituted forWelbeckat 78'minutes
- 10RooneySubstituted forHernándezat 77'minutes
- 17Almeida da Cunha
- Lee Mason
- Shots on Target
Second Half ends, West Ham United 0, Manchester United 2.
Darren Fletcher (Manchester United) wins a free kick in the defensive half.
Foul by Antonio Nocerino (West Ham United).
Delay over. They are ready to continue.
Delay in match James Tomkins (West Ham United) because of an injury.
Substitution, West Ham United. Antonio Nocerino replaces Matthew Taylor.
Corner, West Ham United. Conceded by Marouane Fellaini.
Substitution, Manchester United. Danny Welbeck replaces Juan Mata.
Substitution, Manchester United. Javier Hernández replaces Wayne Rooney.
Corner, Manchester United. Conceded by Guy Demel.
Ashley Young (Manchester United) wins a free kick in the defensive half.
Foul by George McCartney (West Ham United).
Substitution, West Ham United. Carlton Cole replaces Kevin Nolan.
Offside, Manchester United. Shinji Kagawa tries a through ball, but Wayne Rooney is caught offside.
Michael Carrick (Manchester United) wins a free kick in the defensive half.
Foul by Kevin Nolan (West Ham United).
Hand ball by Marouane Fellaini (Manchester United).
Attempt missed. Alexander Büttner (Manchester United) left footed shot from outside the box is high and wide to the left. Assisted by Shinji Kagawa.
Corner, Manchester United. Conceded by George McCartney.