With relentless Manchester City winning at Everton in the earlier kickoff to move four points clear, long-time league leaders Arsenal knew only a victory would suffice.
But they produced a laboured display against the crafty south coast club and were outplayed after the break as Julio Enciso, Deniz Undav and Pervis Estupinan scored for Roberto De Zerbi's side, putting City on the brink of securing the title.
The result also moved Brighton up to sixth place with games in hand on the teams around them.
Arsenal's former Brighton forward Leandro Trossard struck the crossbar in the first half, but Arsenal looked deflated after Enciso struck in the 51st minute and crestfallen when Undav lobbed over Aaron Ramsdale in the 86th minute.
Estupinan completed Arsenal's misery in stoppage time to the delight of Brighton's fans who may soon be watching the club's first venture into European competition.
A fifth league defeat of the season left Arsenal on 81 points with two games remaining to City's 85 with three left, meaning victory for Pep Guardiola's side next Sunday against Chelsea would wrap up City's fifth title in six seasons.
City could even secure it before that if Arsenal lose against Nottingham Forest on Saturday.
Brighton have 58 points with four games still remaining.
"Yeah it looks difficult now to be honest, we have to be realistic. I don't think City are going to do too many mistakes now," Arsenal captain Martin Odegaard said.
"It is not a good feeling at the moment. The way we played, particularly in the second half, I don't know what happened to be honest. It feels like there is no hope now."
There was a hint of resignation in the air amongst Arsenal's fans as they streamed towards the Emirates Stadium after hearing of Manchester City's earlier 3-0 victory at Everton -- an 11th successive league win for City.
And there was a lethargy about Arsenal's play as Brighton sucked the life out of them with their measured passing game.
Arsenal were not helped by losing forward Gabriel Martinelli to injury midway through the first half after he failed to shake off the effects of a hefty Moises Caicedo tackle.
The Brazilian was replaced by Trossard, who came closest to breaking the deadlock before halftime with a shot that clipped the top of the crossbar.
Odegaard drilled a shot just wide and Bukayo Saka did the same in first-half stoppage time, but Brighton hogged possession and were always a threat with Enciso twice having a clear sight of goal.
The home fans tried to galvanise their team but the mood fell flat six minutes after the interval as Brighton attacked down the left and after his initial cross was blocked, Estupinan lifted a ball into the area for Enciso to head in.
Arsenal never looked convincing as they tried to respond and shot themselves in the foot when Ramsdale passed the ball out to Trossard and his flick rebounded back towards goal, giving Undav all the time in the world to lob the ball into the net.
Brighton & Hove Albion's Deniz Undav celebrates scoring their second goal - Premier League - Arsenal v Brighton & Hove Albion - Emirates Stadium, London, Britain - May 14, 2023. (Photo: Action Images via Reuters)
With Arsenal in tatters, Estupinan put the icing on Brighton's cake, steering in a rebound after Ramsdale had parried Undav's powerful shot.
While defeat stung for Arteta's side, the damage had really already been done last month when they drew with Liverpool and West Ham, having led in each game by two goals, and then drew 3-3 at home to relegation-bound Southampton.
Those results handed the initiative to City who have churned out points with ruthless efficiency.
While City have taken 40 points from the last 42 on offer, Arsenal's brave challenge for a first title since 2004 has unravelled in disappointing fashion as the pressure mounted.