Watford went into the first half leading the Clarets, and deservedly so. James Tarkowski could not do much when the ball bounced off him to give the Hornets an early lead.
That lead lasted nearly 80 minutes. Jack Cork, however, put an end to it when he was left unmarked in the 83rd minute to deny Watford what would have been a massive three points. Indeed, it would only get worse for Roy Hodgson's men when Josh Brownhill slotted the ball past Ben Foster to take all three points back to Lancashire.
That result puts Burnley above Leeds United on goal difference, and takes them five points above 18th-placed Everton. Watford are now twelve points adrift with just four games remaining, all but confirming Championship football for the Hertfordshire-side next season.
Burnley's victory also confirmed Norwich City's relegation from the top flight.
Story of the game
Watford vs Burnley is not a game on the calendar that many a football enthusiast would highlight for viewing. But Saturday's fixture proved an entertaining clash between two sides desperate to secure their survival in the top flight.
Watford, a side who have frequently failed to come out roaring from the off, moved fast down the left-hand side with Hassane Kamara in the opening seconds, whose cross was an easy catch for Nick Pope. However, it signalled what was to come from the match.
The side looked keen to operate a high and tight press on Burnley, forcing their opposition into errors which they did not look to have expected.
In the 8th minute, the aftermath of a Watford corner found Kiko Femenia on the edge of the penalty box, who whipped the ball in. A slight deflection from Connor Roberts guided it on to Juraj Kucka, who blasted the ball at the crossbar, bouncing out and hitting James Tarkowski. He could only watch on as the ball spilled into the back of the net.
With only three clean sheets all season, of which only one had been a 1-0 victory - at Aston Villa in February - the Hornets knew they would need to press for a second goal. And so they did.
Burnley were still failing to get tight enough to Watford. In the 11th minute Kucka was left in acres of space, but could only guide his header over. In the 13th minute, again he found himself unmarked in the penalty area. Tarkowski made amends to his earlier own goal by blocking the goal-bound shot.
Watford's high intensity continued two minutes later. Ben Foster launched the ball upfield where he found Joao Pedro, who could not work his shot on target; launching the ball over the crossbar and denying the 39-year-old goalkeeper his second assist of the season.
Burnley finally started to find their feet around the 20th minute. Josh Brownhill directed a half volley just wide of Foster's right-hand post, sending a warning the Golden Boys.
With Watford's phase of attack beginning to cede, Dwight McNeil thought he had won the Clarets a penalty when Craig Pawson pointed to the spot after a clever run by the winger. A VAR check, however, confirmed that the Englishman had been centimetres outside the penalty area when he was clipped by Moussa Sissoko. The resulting free-kick posed no threat to the Hornets.
As the end of the first half came, Watford began to find their mojo again. Emmanuel Dennis, the hosts' top scorer this season, forced a tight save from Nick Pope at his near post from what had looked like an impossible angle for the Nigerian.
On the brink of half time, he thought he was through again, only to be prevented from a one-on-one situation thanks to some clever defending from Charlie Taylor.
So far, so good at the break for Watford. But, as any fan will know, a one goal advantage can most certainly be usurped at Vicarage Road.
The second half was much the opposite to the first. Burnley were the ones that came out of the blocks quickly. Aaron Lennon should have scored within the opening minute of the second half, but failed to put the ball past an on-rushing Foster from the middle of the box.
Michael Jackson's men, who had picked up an impressive seven points from a possible nine under their new interim manager, immediately appeared far better organised in the second forty-five. Watford's tightness also appeared to disappear, their intensity dropping.
Nonetheless, in the 50th-minute there was another huge chance for the Hornets to give themselves a two-goal cushion. On a counter-attack, Joao Pedro found Ismaila Sarr, who found Emannuel Dennis on the left. Once more, Kucka was in space and his resultant shot forced a smart save from Pope.
A substitution in the 60th-minute gave Burnley their intensity back. Ashley Barnes, who has featured far less this season than in previous years, came on to replace new signing Wout Weghorst. It appeared a surprise - but gives credit to Jackson's fast developing managerial credentials.
The Lancashire side continued to threaten Watford on their own turf. Roy Hodgson's team appeared comfortable to sit back and defend in order not open themselves up to attack for a while. Yet again, that proved not to work.
In the 73rd-minute, Foster made an outstanding save from Barnes in what gave some Watford fans the re-assurances that they may just hold out for a win. He pushed the Austrian's header onto the crossbar, before pouncing it out as the ball was cleared. The threat continued to grow when Josh Brownhill's shot was blocked on the edge of the area two minutes later.
With 17 goals conceded this season in the last fifteen minutes, Watford are by far one of the most prone teams to conceding late on - with only Norwich (18) conceding more. That form would strike again.
In the 83rd minute, Taylor whipped in a fine ball from the right-hand side which found Jack Cork in the six-yard box. With the midfielder unmarked, he only had to meet the ball - to which he did, heading into the open net in front of him.
As if things could not get much worse for the Hornets, Burnley struck again four minutes later. Lacklustre defending on the edge of the area meant the ball fell to Brownhill. This time, he did not miss - slotting comfortably past Foster's left-hand side, and sending the away fans into hysterics.
The referee's full-time whistle was met with what has become a regular feature of boos from the home supporters - or what was left of them. Saturday's defeat marks the longest ever losing streak at home in the history of English football for Watford. That is a run which sums up a dire season for the Hornets as they prepare yet again for Championship football.
The result will also put a huge sweat on the face of Everton manager Frank Lampard. There is now a serious possibility that the Merseyside team will be playing second-tier football next season for the first time in seventy years.
Watford: Foster; Femenia, Kabasele, Samir, Kamara; Sissoko, Louza, Kucka; Sarr, Joao Pedro, Dennis.
Unused subs: Bachmann, Ngakia, Troost-Ekong, King, Masina, Sema, Gosling, Kalu, Kayembe.
Burnley: Pope; Roberts, Collins, Tarkowski, Taylor; McNeil, Cork, Brownhill, Lennon (Lowton 89'); Vydra (Stephens 90+2'), Weghorst (Barnes 60').
Unused subs: Hennessey, Bardsley, Long, Thomas, Costelloe.
Referee: Craig Pawson
Burnley, meanwhile, continue their charge away from the relegation zone as they host Aston Villa next Saturday.