In the worst blunder in Oscar history, the Academy Award for best picture was handed to the wrong nominee - and the mistake was only discovered halfway through the acceptance speech.
Faye Dunaway announced the wrong winner for best picture at the end of the night, awarding the trophy to La La Land when it actually was supposed to go to Moonlight.
Moonlight director Barry Jenkins said he was "speechless" when the correct result was offered.
It all started as Dunaway's co-presenter, Warren Beatty, opened the envelope to read the winner for best picture. He looked confused, took a long pause, and then looked over at Dunaway, who clearly thought he was doing some sort of bit.
"You're awful!" she said, as the crowd laughed nervously. "God."
Beatty then handed the envelope to Dunaway, who announced "La La Land!"
The cast and crew of La La Land arrived on stage to accept the award before someone realised the mix-up, which set off moments of extreme confusion, slight panic and...well, no one really knew what was happening.
"There's been a mistake," producer Jordan Horowitz said, as he ran onstage. "Moonlight, you guys won."
As Beatty later explained to the crowd, he had paused to look at the envelope, which read "Emma Stone, La La Land." Stone had just won best actress.
"That's why I took such a long look at Faye...I wasn't trying to be funny," Beatty explained to the audience. "This is Moonlight the best picture."
La La Land's cast and crew were halfway through their acceptance speeches when the mistake was realised.
Host Jimmy Kimmel joked: "Warren, what did you do?"
The Washington Post described it as the most shocking Oscars moment ever and the error was quickly picked up as a topic of discussion by viewers.
Afterwards, Emma Stone spoke to reporters backstage:
"Of course it was an amazing thing to hear La La Land. We would have loved to have won best picture. But we are so excited for Moonlight. I think it's one of the best films of all time.
"I was also holding my 'best actress in a leading role' card that entire time. So whatever story, I don't mean to start stuff, but whatever story that was, I had that card."
Moonlight director Jenkins said he's a longtime Oscar viewer, and had never seen anything like this happen before.
"I noticed the commotion and I thought something strange had occurred, and I'm sure everybody saw my face, but I was speechless when the result was offered," Jenkins said backstage.
"So it made a very special feeling even more special, but not in the way I expected."
Wow and we thought @realDonaldTrump was going to be the most controversial thing about the #Oscars
— Hilary Barry (@Hilary_Barry) February 27, 2017
Should have gone to Specsavers. #Oscars
— Philip Matthews (@secondzeit) February 27, 2017
Holy crap #Oscars
— Kim Choe (@kimchoe) February 27, 2017
RT if you're having the same reaction rn. #Moonlight #Oscars pic.twitter.com/69SvdPoQcL
— People (@people) February 27, 2017
We have no idea what just happened, but #Moonlight is the Oscar winner for Best Picture. Let's celebrate! https://t.co/PO5wISIHSA pic.twitter.com/IGFucXaOFf
— IndieWire (@IndieWire) February 27, 2017
Additional reporting: Washington Post