Match ends, Celtic 1, Motherwell 2.
Motherwell won at Celtic Park for the first time in nearly eight years, coming from behind to do so.
Louis Moult's double turned the game around after Nir Bitton's deflected shot had given the champions the lead.
It means Celtic have failed to win at home in their last four games, the first time that has happened since Tony Mowbray was manager.
They remain a point clear of Aberdeen at the top of the league, while Well's revival under Mark McGhee continues.
The match was prefaced by an emotional unveiling of a statue of Celtic's legendary European Cup-winning captain, Billy McNeill.
The thousands of supporters who gathered for the occasion would have been underwhelmed by what unfolded inside the stadium in the opening 45 minutes.
Their team dominated possession but found Motherwell to be well organised and therefore difficult to penetrate.
But the chess-like approach to the first half could not have been in greater contrast to the action-packed second period.
Lionel Ainsworth should have put Motherwell ahead, but his chip over goalkeeper Craig Gordon also cleared the crossbar.
It looked like Motherwell would pay a hefty price for that as Tom Rogic burst clear, squared for Bitton and the midfielder's shot took a big deflection off Keith Lasley on its way past goalkeeper Connor Ripley.
However, Marvin Johnson, whose pace had already caused Celtic problems, soon fired the ball across goal for Moult to tap into the net.
And the game was turned on its head when Scott McDonald's sharp turn enticed Jozo Simunovic into a rash challenge.
It gave Moult the opportunity to double his and Motherwell's tally, which he duly took, rolling the penalty straight down the middle as Gordon dived to his left.
They could have gone further ahead but for Gordon, who rushed off his line to block from McDonald after Dedryck Boyata got into trouble and then used his left foot to deny Moult a hat-trick.
In between those efforts, Bitton had a shot blocked on the line and Ripley saved from Scott Allan and Kris Commons.
Celtic piled forward in the closing stages but failed to create any further openings as Motherwell celebrated a hard-earned victory.
- 6BittonBooked at 78mins
- 18RogicSubstituted forColeat 74'minutes
- 49ForrestSubstituted forAllanat 67'minutes
- 6McManusSubstituted forLaingat 77'minutes
- 4GrimshawSubstituted forAinsworthat 45'minutesSubstituted forWattat 81'minutes
- Bobby Madden
- Shots on Target
Second Half ends, Celtic 1, Motherwell 2.
Corner, Celtic. Conceded by Luke Watt.
Callum McGregor (Celtic) wins a free kick in the defensive half.
Foul by Marvin Johnson (Motherwell).
Attempt blocked. Kris Commons (Celtic) right footed shot from outside the box is blocked.
Kieran Tierney (Celtic) wins a free kick in the attacking half.
Foul by Louis Moult (Motherwell).
Attempt saved. Kris Commons (Celtic) left footed shot from outside the box is saved in the centre of the goal.
Scott Allan (Celtic) wins a free kick in the defensive half.
Foul by Keith Lasley (Motherwell).
Foul by Nadir Ciftci (Celtic).
Ben Hall (Motherwell) wins a free kick in the defensive half.
Attempt missed. Jozo Simunovic (Celtic) right footed shot from outside the box misses to the right.
Substitution, Motherwell. Luke Watt replaces Lionel Ainsworth.
Attempt saved. Marvin Johnson (Motherwell) right footed shot from the centre of the box is saved in the centre of the goal.
Corner, Celtic. Conceded by Connor Ripley.
Attempt saved. Kris Commons (Celtic) right footed shot from outside the box is saved in the top right corner.
Nir Bitton (Celtic) is shown the yellow card for a bad foul.
Foul by Nir Bitton (Celtic).