Havant and Waterlooville secured a dream FA Cup fourth-round tie against Liverpool after beating Swansea in a thrilling third-round replay.
Rocky Baptiste's tap-in put Havant & Waterlooville 3-0 up
Garry Monk's headed own goal put the Blue Square South side a goal up before a Jamie Collins bundled effort and Rocky Baptiste's tap-in made it 3-0.
Swansea replied with a Guillem Bauza strike before the break, and then Leon Britton saw his penalty saved.
Jason Scotland cut the deficit to one, but Tom Jordan's header sealed victory.
Crowd congestion at the compact Westleigh Park stadium caused a slight delay in the kick-off, and a few of the fans were still making their way through the turnstiles when Havant - three divisions below their opponents - took a shock lead.
Brett Poate, who was sent off in the first tie, collected a short corner on the right wing and delivered a wicked in-swinging cross towards Swansea's front post.
Monk dived forward under pressure from home striker Richard Pacquette, but the centre-back only managed to head the ball into his own net.
Swansea almost found an immediate response as striker Bauza sent a deft chip over advancing Havant goalkeeper Kevin Scriven just wide of the post.
Scriven then produced a fine save to push Andy Robinson's low drive - which took a slight deflection off Bauza - for a corner.
Swansea's superior class began to tell as they pushed the home side back to the edge of their penalty area, but indecisive defending and poor goalkeeping allowed Havant to double their lead on 25 minutes.
Left-back Marcus Painter gave away a needless corner and, after a poor clearing punch from goalkeeper Dorus De Vries, Collins' shot through a crowded area found its way into the Swansea net.
The home side, a massive 83 places below League One leaders Swansea in the English pyramid, were in dreamland 13 minutes later when Baptise put them 3-0 up.
Again, the Swansea defence looked under little pressure but Pacquette's miss-hit low shot from outside the area found its way to the far post and Baptiste sneaked around the back to tap the ball home.
The three-goal advantage lasted about a minute as Bauza's fierce 20-yard drive, aided by a slight deflection, nestled into the Havant net.
There was still time for yet more drama in a remarkable first-half as Swansea wasted two golden opportunities to score.
Midfielder Britton was the biggest culprit when his poor penalty, awarded after a foul on Bauza, was comfortably saved by Scriven.
And then defender Dennis Lawrence's downward header from just six yards bounced over the crossbar.
Havant were themselves guilty of wastefulness in the opening seconds of the second half as Pacquette, left unmarked inside Swansea's six-yard box, hit his shot straight at De Vries.
The miss took even greater significance just two minutes later when Swansea closed the deficit to 3-2.
Robinson, whose mazy runs were a constant threat, delivered a pin-point cross which Bauza volleyed against the post, but Scotland was perfectly placed to tap the ball home.
A Swansea equaliser looked inevitable as they continued to dominate possession, but their defensive frailties were again exposed as Havant scored their fourth on 65 minutes.
Brett Poate sent a regulation cross into the centre of Swansea's penalty area but substitute Jordan, son of former Scotland striker Joe, beat his marker to glance a header off the back of his head into the bottom corner.
Jordan almost sealed the win moments later when his looping header came down the wrong side of the crossbar.
The constant entertainment continued as Swansea then hit the woodwork twice in six minutes, substitute Tom Butler denied by the post from a tight angle before Britton's left-footed effort rebounded off the bar to safety.
Robinson then hit the post in stoppage time, and that proved to be the final threat as Havant held on to record a dramatic and famous FA Cup victory.
Havant and Waterlooville: Scriven, Gregory, Warner, Smith (Jordan 46), Poate, Potter, Oatway (Wilkinson 43), Collins, Harkin, Baptiste, Pacquette (Slabber 77).
Subs Not Used: Taylor, Taggart.
Booked: Potter, Collins, Warner.
Goals: Monk 4 og, Collins 25, Baptiste 37, Jordan 65.
Swansea: De Vries, Rangel, Lawrence, Monk, Painter (Duffy 77), Anderson (Butler 51), Pratley, Britton, Robinson, Scotland, Bauza.
Subs Not Used: Knight, Austin, O'Leary.
Booked: Pratley, Butler.
Goals: Bauza 39, Scotland 48.
Ref: Andy D'Urso (Essex).
BBC Sport Player Rater man of the match: Havant's Kevin Scriven 8.22 (on 90 minutes).
Please note that you can still give the players marks out of 10 on BBC Sport's Player Rater after the match has finished.