Reading reached the semi-finals of the Women's FA Cup as Rakel Honnudottir's last-gasp goal beat Manchester United.
After 90 goalless minutes, Reading hit back from trailing twice in extra time.
Alex Greenwood's penalty put United 1-0 up and Remi Allen's header made it 1-1, before Natasha Harding's own goal was equalised by Rachel Furness' strike.
But Iceland forward Honnudottir bundled the ball in on 120 minutes to see Reading join Chelsea, West Ham United and Manchester City in the last four.
- Elsewhere: Man City ease past Liverpool to reach semi-finals
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- Holders Chelsea narrowly beat part-time Durham
The game sparked to life when United were awarded a penalty as Maz Pacheco fouled Lauren James in the area, and Greenwood's cool subsequent penalty was the first of five goals in 22 minutes.
The hosts' veteran England midfielder Fara Williams thought she had won the game towards the end of extra time, as she netted direct from a corner, but her effort was ruled out by the officials for an infringement in the middle.
But Reading, who were competing at the quarter-final stage for the first time since a 3-0 loss at Sunderland in 2016, eventually found a way through from close range thanks to substitute Honnudottir, after England stopper Siobhan Chamberlain's handling error.
Casey Stoney's in-form United had been bidding to reach a second domestic semi-final in what is their first season since reforming a women's side last summer.
Instead, Kelly Chambers' Royals - who are seventh in the top tier - progressed to the Women's FA Cup semi-finals for the first time.
The draw for the last four will be held on Monday, live on BBC Breakfast on BBC One, shortly after 08:30 GMT.
Reading manager Kelly Chambers: "My heart was pounding and racing all at the same time, but to win the game the way we did, showing the belief and passion to keep going, was absolutely fantastic.
"I believe we controlled the game from start to finish, and we created some great chances in the 90 minutes but we just couldn't put them away.
"We had a really positive chat at the end of normal time about staying calm, and we did that - certainly in front of goal - in extra time.
"We'll look forward to the draw and whoever we get, it'll be one to enjoy and with a fabulous incentive of playing in an FA Cup final at the end of it."
Manchester United boss Casey Stoney: "We're bitterly disappointed as a team and a club that we've gone in front twice, and we haven't learnt and then gone on to lose in the last minute - the players are gutted.
"We showed in spells what we are capable of. Did we play at our best? No - we weren't anywhere near the level we know we can operate at.
"But I can't fault the effort and we dealt with most things that came our way. I have a young side here with lots of players who are still learning and developing, and we'll take the positives.
"We've got an average age of 20, 21 and we'll use this experience to fuel the rest of our season, where the league now means everything."
Reading: Moloney, Pacheco (Bailey 120), Williams, Bartrip, Furness, Allen, Bruton, Harding, Moore, Chaplen (Honnudottir 80), Potter.
Subs not used: Pearce, Farrow, Estcourt, Howard, Laws.
Manchester United: Chamberlain, Harris, A Turner, M Turner, Greenwood, Zelem, Green, Toone, Hanson, Sigsworth, Galton.
Subs not used: Ramsey, Arnot, Palmer, Devlin, James, Smith.
Referee: Will Finnie