The Swedish striker struck early in each half as Jose Mourinho’s side pursued their recent upturn in form to move alongside fifth-place Tottenham Hotspur on 30 points in the Premier League table.
United are now just three points off the four Champions League qualifying places, albeit having played a game more than third-place Arsenal and fourth-place Manchester City, who meet on Sunday.
Ibrahimovic put his team on course for victory in the fifth minute at The Hawthorns when he finished off a splendid move in style.France international Paul Pogba, who dominated midfield throughout, set the ball rolling with a crossfield pass to right-back Antonio Valencia.
Valencia’s lofted pass sent Jesse Lingard hurtling past left-back Allan Nyom before a wonderful, pinpoint cross eluded Gareth McAuley and allowed Ibrahimovic to nod past Ben Foster from 10 yards.
Wayne Rooney came close to doubling the lead when his goal-bound header was blocked by Craig Dawson.
He would have been forgiven for thinking he had equalled the watching Bobby Charlton’s all-time record of 249 goals in United colours midway through the first half.
The United captain set his sights on goal from the edge of the penalty box and his powerfully struck, rising shot looked certain to strengthen his team’s grip on proceedings.
But Foster brilliantly tipped the ball onto the crossbar to deny his former England and United colleague a moment of history.
There was, though, no keeping Ibrahimovic out of the limelight and moments later, Baggies fans demanded his dismissal when the giant forward flattened Dawson with a crude aerial challenge.
The yellow card shown by referee Anthony Taylor was greeted with a chorus of boos.
– Rondon-Rojo flashpoint –
West Brom, currently in seventh place, struggled to make home advantage count, but David de Gea was finally tested when Chris Brunt tried his luck from 20 yards following good work by Nacer Chadli.
Salomon Rondon, who scored a 13-minute hat-trick of headers in the midweek 3-1 defeat of Swansea City, then procured a chance to show he was head and shoulders above United’s defence.
The Venezuelan striker escaped the attentions of centre-backs Marco Rojo and Phil Jones, but nodded Matt Phillips’s cross wide of the target.
Back came United and Lingard, in for the dropped Juan Mata, should have given United a two-goal cushion just before the break.
But the composure he showed when teeing up Ibrahimovic early on deserted him and he shot wildly over with just Foster to beat following Matteo Darmian’s miscue.
It was left to Ibrahimovic to double United’s lead 11 minutes into the second half, but this time he needed the help of Lady Luck to get the better of Foster.
After picking up possession from Rooney just outside the box, the 35-year-old sprang between two defenders before unleashing a low shot that beat Foster with the help of a deflection off Dawson.
Tempers flared briefly when Rondon tangled with Rojo, the West Brom striker appearing to slap the United defender, and both were cautioned.
But there was no knocking Mourinho’s players out of their stride as they defended with discipline and determination.
Ibrahimovic, who now has 16 United goals to his credit, showed his selfish side when he went for goal himself rather than setting up Pogba as United broke and the latter made his disapproval clear to his colleague.
Pogba’s heart would have been in his mouth when the locals, including Albion manager Tony Pulis, screamed for handball after he was struck by McAuley’s header following Chris Brunt’s corner.
But that was as close as the home side got to halting United’s momentum.