Brighton took the lead at the Emirates Stadium when Leandro Trossard turned home a low cross from Enock Mwepu to finish a good move from the visitors.
Arsenal had struggled to create chances but thought they had levelled through a close-range effort from Gabriel Martinelli, only for a lengthy VAR check to cancel out his header.
Brighton doubled their lead through Mwepu’s low drive from the edge of the box following a neat interchange between Trossard and Moises Caicedo.
Arsenal gave themselves hope of salvaging a result as Martin Odegaard’s speculative effort looped up off Danny Welbeck to half the arrears.
The result is a huge blow for Arsenal's Champions League hopes an they have now lost two on the bounce following their 3-0 loss at Crystal Palace last Monday.
For Brighton it was their first win since their 2-0 triumph at Watford way back in February. The win lifts them to 11th in the league standings and in with a chance of achieving their aim of a top 10 finish.
Sonny Turner was at the Emirates Stadium for Sussex World and here's his player ratings
Brighton doubled their lead through Mwepu’s low drive from the edge of the box following a neat interchange between Trossard and Moises Caicedo.
13. Tariq Lamptey- 6
Showed his usual energy, and aided the Brighton right flank in dealing with Arsenal throwing everything at them in the closing minutes.
14. Adam Webster- 6
Added an extra body in the defensive line for Graham Potter’s team, and did well in seeing out the game under immense pressure.