Sir Alex Ferguson was denied victory in his 1,500th and final game in charge of Manchester United as Romelu Lukaku's hat-trick earned West Brom a 5-5 draw.
The champions went 3-0 up through Shinji Kagawa, Jonas Olsson's own goal and Alexander Buttner's fine finish.
James Morrison reduced the deficit and Baggies' substitute Lukaku made it 3-2, before Robin van Persie and Javier Hernandez put United 5-2 ahead.
But Lukaku's late double and Youssouf Mulumbu denied Ferguson a winning end.
Watching his side concede three goals in the space of five minutes late in the game was hardly the finish Ferguson wanted at the end of a magnificent managerial career.
But the retiring Scot still managed a smile and a wave before disappearing down the tunnel for the last time.
Despite the crazy finish at The Hawthorns, United ended the season 11 points clear of Premier League runners-up Manchester City, the most comfortable winning margin since Chelsea beat Arsenal by 12 points in 2004-05.
If Ferguson's official retirement party was at Old Trafford seven days earlier, this was the final goodbye.
Nearly 10,000 days since his first match in charge of United, an inauspicious 2-0 defeat against Oxford United, Ferguson took his place in the dugout for the final time after players from both sides had formed a guard of honour.
Romelu Lukaku joins Emmanuel Adebayor, Robert Earnshaw, Ole Gunnar Solskjaer and Jimmy Floyd Hasselbaink to score a Premier League hat-trick as a substitute
Dressed in blazer and tie, Ferguson acknowledged all four sides of the ground as a sell-out crowd rose in appreciation of the Scottish mastermind who had accumulated 13 league titles, five FA Cups, four League Cups, two European Cups and one Club World Cup during 26 years in charge at Old Trafford.
Ferguson then sat back and watched his much-changed side dismantle West Brom in the opening 30 minutes before the home side roared back to snatch a thrilling point which sees them finish a creditable eighth in the Premier League table.
Though the occasion revolved around the 71-year-old, there was a match to be won and records to be broken.
Ferguson's United record
Lukaku's second-half efforts ultimately denied United a Premier League record 29th win of the season, which would also have seen Ferguson's men equal their best points haul of 91 in the competition.
West Brom's chances of raining on Ferguson's parade seemed slim in the sixth minute when Japan international Kagawa punished some poor defending to nod home Hernandez's cross from close range.
Three minutes later it was 2-0, Olsson steering Antonio Valencia's low cross from the right past Ben Foster.
Such was United's dominance in the first half that there were times when the match had the feel of a pre-season friendly.
Ferguson did not even bother getting out of his seat to celebrate Buttner's 30th-minute goal, a powerful finish from a tight angle by the Dutch full-back after neat work by Tom Cleverley and the impressive Hernandez.
Van Persie leading scorer again
Robin van Persie finishes Premier League top scorer for the second successive season after following up his 30 goals for Arsenal last campaign with 26 for Manchester United during 2012-13
The Baggies reduced the deficit before half-time through James Morrison after he had got ahead of Phil Jones to steer home a cross from the right.
The introduction of Lukaku, on loan from Chelsea, at the start of the second half ultimately proved to be the turning point.
The Belgian found the net with a quality low finish from 20 yards before Robin van Persie's 26th league goal of the campaign, from a cross by Valencia, made it 4-2.
It looked all over when the tireless Hernandez added a fifth by steering home a Ryan Giggs cross.
But after Lukaku converted a neat pass in the 81st minute to bring the hosts back within two goals, Mulumbu made it 5-4 moments later following a cross from the right.
The comeback was completed in the 86th minute when Lukaku bundled the ball over the line from close range at the second attempt after United's defence had failed to clear.
The final whistle was greeted with relief on the United bench, Ferguson just about managing a smile as he made his way from the dugout.
With one final wave, he vanished down the tunnel for the last time.
Truly the end of an era.
West Brom manager Steve Clarke:
"It was a great occasion. That game will be remembered for a long time.
"I am not sure Sir Alex enjoyed it that much, but he was quite complimentary about our season and I wish him all the best.
Clarke on hat-trick scorer Romelu Lukaku:
"Romelu is a Chelsea player and he will go back there. We wish him well. If Chelsea wish to let him out on loan next season then we would love to have him back."
West Bromwich Albion
- 01 Foster
- 03 Olsson
- 06 Ridgewell (Lukaku - 46' )
- 23 McAuley
- 28 Jones
- 05 Yacob
- 07 Morrison (Fortune - 79' )
- 11 Brunt
- 17 Dorrans
- 21 Mulumbu
- 09 Long (Rosenberg - 79' )
- 13 Myhill
- 04 Popov
- 25 Dawson
- 30 Tamas
- 08 Rosenberg
- 20 Lukaku
- 32 Fortune
- 13 Lindegaard
- 04 Jones
- 06 Evans (Ferdinand - 83' )
- 28 Buttner
- 07 Valencia
- 08 Anderson
- 16 Carrick
- 23 Cleverley (Giggs - 60' )
- 26 Kagawa (Scholes - 69' Booked )
- 14 Hernandez
- 20 Van Persie
- 01 De Gea
- 03 Evra
- 05 Ferdinand
- 15 Vidic
- 11 Giggs
- 22 Scholes
- 44 Januzaj
Live Text Commentary
Full Time The referee ends the match.90:00 +3:07
A cross is delivered by Markus Rosenberg.90:00 +1:57
Unfair challenge on Michael Carrick by Marc-Antoine Fortune results in a free kick. Rio Ferdinand takes the indirect free kick.90:00 +1:42
Centre by Ryan Giggs, Ben Foster makes a save.90:00 +1:14
The ball is delivered by Ryan Giggs, clearance by Gareth McAuley.90:00 +1:04
Centre by Antonio Valencia.90:00 +0:23
The referee blows for offside. Indirect free kick taken by Anders Lindegaard.89:40
Ryan Giggs takes a shot. Jonas Olsson gets a block in.89:30
A cross is delivered by Antonio Valencia, clearance made by Graham Dorrans.88:41
Romelu Lukaku delivers the ball, clearance made by Rio Ferdinand.88:25
Marc-Antoine Fortune takes a shot. Blocked by Billy Jones.87:21
Free kick awarded for a foul by Claudio Yacob on Robin van Persie. Ryan Giggs takes the free kick.85:17
Assist by Youssouf Mulumbu.85:17 Goal scored
Goal! - Romelu Lukaku - West Brom 5 - 5 Man Utd Romelu Lukaku finds the back of the net with a goal from close range to the bottom right corner of the goal. West Brom 5-5 Man Utd.84:25
Alexander Buttner is penalised for handball and concedes a free kick. Indirect free kick taken by Ben Foster.84:15
The ball is crossed by Antonio Valencia, Claudio Yacob makes a clearance.83:16
Foul by Romelu Lukaku on Michael Carrick, free kick awarded. Indirect free kick taken by Anders Lindegaard.82:02
Free kick taken by Chris Brunt.82:02 Substitution
Substitution Rio Ferdinand joins the action as a substitute, replacing Jonny Evans.82:02 Booking
Booking Paul Scholes goes into the referee's book for unsporting behaviour.
Free kick awarded for a foul by Paul Scholes on Claudio Yacob.80:50
Assist by Billy Jones.80:50 Goal scored
Goal! - Youssouf Mulumbu - West Brom 4 - 5 Man Utd Youssouf Mulumbu grabs a goal from inside the penalty area to the bottom left corner of the goal. West Brom 4-5 Man Utd.80:03
Assist by Markus Rosenberg.80:03 Goal scored
Goal! - Romelu Lukaku - West Brom 3 - 5 Man Utd Romelu Lukaku finds the back of the net with a goal from just inside the area to the bottom left corner of the goal. West Brom 3-5 Man Utd.79:21
Billy Jones takes a shot. Ben Foster makes a save.79:08
Centre by Chris Brunt, clearance by Alexander Buttner.78:05 Substitution
Substitution Markus Rosenberg is brought on as a substitute for Shane Long.78:05 Substitution
Substitution (West Brom) makes a substitution, with Marc-Antoine Fortune coming on for James Morrison.77:39
Antonio Valencia delivers the ball, Effort on goal by Ryan Giggs from just inside the area clears the bar.76:34
Graham Dorrans produces a right-footed shot from inside the area that goes over the bar.76:01
Alexander Buttner delivers the ball.74:25
James Morrison crosses the ball, Romelu Lukaku has an effort at goal from just inside the box that misses to the left of the goal.73:17
The ball is crossed by Chris Brunt, clearance made by Jonny Evans.72:53
Short corner taken by Chris Brunt.70:10
Corner taken left-footed by Chris Brunt from the right by-line, Jonny Evans makes a clearance.69:26
Unfair challenge on Billy Jones by Paul Scholes results in a free kick. Romelu Lukaku takes the direct free kick.69:12
The ball is sent over by Romelu Lukaku.68:20 Substitution
Substitution Paul Scholes comes on in place of Shinji Kagawa.68:06
Effort on goal by Graham Dorrans from outside the area goes harmlessly over the bar.67:58
Claudio Yacob produces a cross, Phil Jones makes a clearance.67:22
Free kick awarded for an unfair challenge on Shane Long by Alexander Buttner. Chris Brunt takes the direct free kick.66:27
Close range effort by Jonas Olsson goes over the bar.65:58
Short corner taken by Chris Brunt.65:03
The ball is delivered by Antonio Valencia.64:03
Outswinging corner taken left-footed by Ryan Giggs played to the near post, Romelu Lukaku makes a clearance.62:39
Assist by Ryan Giggs.62:39 Goal scored
Goal! - Javier Hernandez - West Brom 2 - 5 Man Utd Javier Hernandez gets on the score sheet with a goal from close in to the bottom right corner of the goal. West Brom 2-5 Man Utd.59:16 Substitution
Substitution Ryan Giggs comes on in place of Tom Cleverley.59:03
Shot by Graham Dorrans from outside the box goes over the net.58:40
The ball is crossed by Youssouf Mulumbu, Antonio Valencia makes a clearance.57:44
Unfair challenge on Shane Long by Phil Jones results in a free kick. Direct free kick taken by Graham Dorrans.55:37
The ball is crossed by Michael Carrick, Javier Hernandez takes a shot. Blocked by Gareth McAuley.54:55
Corner taken left-footed by Robin van Persie from the right by-line, clearance made by Gareth McAuley.54:01
The referee blows for offside. Indirect free kick taken by Michael Carrick.53:37
The ball is delivered by Shane Long.52:37
Antonio Valencia provided the assist for the goal.52:37 Goal scored
Goal! - Robin van Persie - West Brom 2 - 4 Man Utd Robin van Persie finds the net with a goal from inside the box to the top right corner of the goal. West Brom 2-4 Man Utd.52:37
The ball is sent over by Antonio Valencia,52:08
The ball is crossed by James Morrison, save made by Anders Lindegaard.52:00
Chris Brunt crosses the ball.51:01
Antonio Valencia delivers the ball.49:14 Goal scored
Goal! - Romelu Lukaku - West Brom 2 - 3 Man Utd Romelu Lukaku scores a goal from outside the penalty area to the bottom right corner of the goal. West Brom 2-3 Man Utd.47:35
Unfair challenge on Javier Hernandez by Gareth McAuley results in a free kick. Tom Cleverley restarts play with the free kick.46:23
Free kick awarded for an unfair challenge on Jonny Evans by Shane Long. Free kick taken by Anders Lindegaard.46:06
The ball is sent over by Alexander Buttner, save made by Ben Foster.45:53
Alexander Buttner crosses the ball, clearance made by Jonas Olsson.45:01
The referee blows his whistle to start the second half.45:01 Substitution
Substitution Romelu Lukaku is brought on as a substitute for Liam Ridgewell.45:00 +2:42 Half time
Half Time The players leave the pitch at half time.45:00 +1:44
Tom Cleverley takes a inswinging corner.45:00 +1:00
The ball is crossed by James Morrison, save by Anders Lindegaard.45:00 +0:35
Shane Long takes a shot. Jonny Evans gets a block in.45:00 +0:08
Free kick awarded for a foul by Claudio Yacob on Shinji Kagawa. Shinji Kagawa restarts play with the free kick.43:50
Unfair challenge on Tom Cleverley by Shane Long results in a free kick. Jonny Evans takes the indirect free kick.43:05
The ball is crossed by Robin van Persie.42:50
Robin van Persie decides to take the corner short.42:23
Javier Hernandez takes a shot. Blocked by Ben Foster.41:39
Javier Hernandez is flagged offside by the assistant referee. Ben Foster takes the free kick.39:46
Assist by Graham Dorrans.39:46 Goal scored
Goal! - James Morrison - West Brom 1 - 3 Man Utd A goal is scored by James Morrison from inside the penalty area to the bottom right corner of the goal. West Brom 1-3 Man Utd.38:02
The ball is swung over by Antonio Valencia, Javier Hernandez produces a right-footed shot from deep inside the penalty box which goes wide of the left-hand upright.37:56
The ball is sent over by Oliveira Anderson.36:38
The assistant referee flags for offside against Javier Hernandez. Indirect free kick taken by Ben Foster.36:10
Foul by Chris Brunt on Javier Hernandez, free kick awarded. Javier Hernandez takes the free kick.35:37
Unfair challenge on Shinji Kagawa by Claudio Yacob results in a free kick. Indirect free kick taken by Anders Lindegaard.35:27
The ball is delivered by Youssouf Mulumbu, clearance made by Jonny Evans.34:21
Billy Jones produces a cross.34:05
Graham Dorrans sends in a cross, clearance by Phil Jones.33:28
Javier Hernandez gives away a free kick for an unfair challenge on Jonas Olsson. Youssouf Mulumbu restarts play with the free kick.31:27
Shane Long has a header from close in and clears the crossbar.29:34
The assist for the goal came from Tom Cleverley.29:34 Goal scored
Goal! - Alexander Buttner - West Brom 0 - 3 Man Utd Alexander Buttner gets on the score sheet with a goal from inside the box to the bottom right corner of the goal. West Brom 0-3 Man Utd.28:03
Antonio Valencia delivers the ball, clearance by Jonas Olsson.26:10
The ball is sent over by James Morrison.25:09
Liam Ridgewell crosses the ball, clearance made by Jonny Evans.23:40
Michael Carrick delivers the ball, Header from close range by Javier Hernandez misses to the right of the target.23:29
Alexander Buttner sends in a cross.22:30
Long range shot from Graham Dorrans misses to the left of the goal.18:23
Jonny Evans challenges Shane Long unfairly and gives away a free kick. Chris Brunt takes the free kick.14:36
James Morrison is ruled offside. Michael Carrick takes the free kick.13:34
Corner taken by Tom Cleverley from the left by-line to the near post, Robin van Persie takes a shot. Jonas Olsson gets a block in.13:07
Robin van Persie takes a shot. Jonas Olsson gets a block in.8:30
Assist on the goal came from Antonio Valencia.8:30 Goal scored
Goal! - Jonas Olsson - West Brom 0 - 2 Man Utd Jonas Olsson scores an own goal from 12 yards. West Brom 0-2 Man Utd.8:27
Antonio Valencia takes a shot.7:34
The offside flag is raised against Shane Long. Indirect free kick taken by Michael Carrick.5:09
Javier Hernandez provided the assist for the goal.5:09 Goal scored
Goal! - Shinji Kagawa - West Brom 0 - 1 Man Utd Shinji Kagawa scores a headed goal from close in. West Brom 0-1 Man Utd.4:44
Shane Long produces a cross, Michael Carrick manages to make a clearance.0:13
Liam Ridgewell concedes a free kick for a foul on Phil Jones. Indirect free kick taken by Anders Lindegaard.0:00
The referee starts the match.
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