ALBION became only the fourth team to take a point off the Barclays Premier League leaders this term with a brilliant Boxing Day display.
The Baggies had to dig in for long spells as City's expensively-assembled side attempted to keep their two-point lead intact over neighbours United.
But Roy Hodgson's men stood up to the task and created as many clear-cut chances as the visitors, with both teams hitting the woodwork in the second half through Mario Balotelli and Jerome Thomas efforts.
Albion's fourth league clean sheet of the campaign saw them become the first team to stop City scoring in the Barclays Premier League this season.
And it helped them build on a terrific week on the road after their back-to-back wins at Blackburn and Newcastle.
Billy Jones was handed his first start in seven games as Hodgson made one enforced due to Steven Reid's injury, which also paved the way for Gonzalo Jara Reyes, recalled from a loan spell at Brighton last week, to return to the bench.
Roberto Mancini made four changes as Pablo Zabaleta, James Milner, Kolo Toure and Balotelli came in for the injured Micah Richards and benched trio Gareth Barry, Joleon Lescott and Adam Johnson.
A packed Hawthorns - including One Direction star and lifelong Baggies fan, Liam Payne - pumped up the volume as the game got underway and the hosts went mightily close to snatching a third-minute lead.
A swift counter-attack resulted in Thomas feeding Chris Brunt and the skipper swivelled 20 yards out before drilling just wide of the far post.
City began to keep Albion pegged back by playing long spells of keep-ball but they didn't threaten the Baggies' goal until the 13th minute, when Milner headed weakly wide from Gael Clichy's left-wing centre.
Less than 60 seconds later, Samir Nasri went much closer with a 20-yard snapshot but Ben Foster was equal to it, clutching the ball at the foot of his right-hand post.
Paul Scharner, fresh from his match-winner at Newcastle last Wednesday, was hungry for more goals and his 25-yard grass-cutter forced a fine save from Joe Hart at his near post.
But the league leaders should have been ahead on 25 when David Silva, arguably the leading candidate for the player-of-the-season award, exchanged a one-two with Sergio Aguero before lofting the ball over from 12 yards.
Aguero proved a real handful a minute later when he skipped past Gareth McAuley and Scharner before being dispossessed by Jones in the nick of time as he shaped to shoot.
Balotelli had had a quiet game thus far but went close in the 29th minute when he saw a 25-yard free-kick clip the Albion wall and bounce just wide of Foster's left-hand post.
The pattern of the game had not changed from the first whistle, with Mancini's men prodding and probing for a goal while Albion, from scraps of possession, did their best to pose a threat.
On 33, Balotelli made room for a shot in the Albion 'D' but Foster's handling was again safe as houses, clutching the curling effort low to his left.
But Albion were defending and grafting manfully and, after City conceded possession deep in the Baggies' half, they broke purposefully. Only Vincent Kompany's outstretched boot denied Shane Long a simple chance from Brunt's dangerous centre.
That proved the final action of a largely uneventful half which City had dominated but failed to seriously test Foster's goal.
The second half continued in similar vein - but Albion had a real let off in the 54th minute.
Balotelli tried his luck from what looked an impossible position but ended up smashing Foster's bar with a devilish 30-yard drive.
However, three minutes later, it was the visitors who had a lucky escape.
After a brief spell of Baggies pressure, Thomas whipped a tremendous cross into the box and the unmarked Long headed a great chance inches wide of the left-hand post.
The game was beginning to liven up and a neat one-touch move created a shooting chance for Silva, but the Spaniard shot straight at the perfectly-positioned Foster from 18 yards.
However, Albion had really taken a foothold in the game and it was City's turn to be camped in their own half.
Yet, on 65, McAuley saved Albion's bacon with a wonderfully-timed last-ditch tackle on Aguero, who only had Foster to beat. There was some dispute over whether the Argentina ace was onside when Milner headed the ball into the Baggies box, but TV replays confirmed Nicky Shorey had played him onside.
From the ensuing corner, the ball broke to Kolo Toure who tried his luck from 30 yards, but his effort sailed high into the Smethwick End.
Back came Albion and Brunt fizzed a 25-yard drive just wide from Odemwingie's short free-kick.
At the other end, Jones was having a great game, as was his right-sided defensive partner McAuley, and the latter did well to get in the way of Aguero's angled 15-yard drive and divert the ball wide.
The 73rd minute produced a moment of real Albion agony.
Thomas pounced on the loose ball after City only partially cleared a free-kick and the winger saw his 25-yard half-volley beat Hart but cannon off the far post and to safety.
Albion had to defend for their lives during the closing stages and Olsson protected Foster's goal by throwing himself at Silva's 15-yard shot.
In the final minute, Edin Dzeko headed a half-chance wide from fellow sub Adam Johnson's corner.
But Albion comfortably ran down the clock and the roar of approval from the home hordes at the final whistle was just reward for a terrific team display.
ALBION (4-4-2): Foster; Jones, McAuley, Olsson, Shorey; Thomas, Mulumbu (Dorrans 80), Scharner, Brunt; Odemwingie (Jara Reyes 89), Long. Subs not used: Fulop (gk), Thorne, Fortune, Dawson, Cox.
MAN CITY (4-4-2): Hart; Zabaleta, Kompany, K Toure, Clichy; Milner (Dzeko 83), Silva, Y Toure, Nasri (Barry 59); Aguero (Johnson 75), Balotelli. Subs not used: Pantilimon (gk), Lescott, Savic, De Jong.
BOOKINGS: MAN CITY - Yaya Toure (foul 69).
REFEREE: L Mason (Lancashire).
ALBION STARMAN: Billy Jones.