The Hammers now drop to a dangerous 17th in the Premier League table, just outside the relegation zone.
The Seagulls dominated proceedings throughout but were helped by a penalty in the 75th minute to give Murray his second goal of the evening after opening the scoring in the 10th minute.
Murray had won the penalty himself, brought to ground by a tiring Pablo Zabaleta, and the spot kick put the game out of the hosts' reach.
José Izquierdo had provided the second goal of the night in the closing seconds of the first half with a tremendous strike from the edge of the box.
Glenn Murray and Bruno Saltor of Brighton and Hove Albion embrace in victory after the Premier League match between West Ham United and Brighton and Hove Albion at London Stadium on October 20, 2017 in London, England
Image credit: Getty Images
TALKING POINT
What next for Slaven Bilic? His team have slipped to 17th, and this was a very poor display. Will he stay in his job? And if not, who's lined up to replace him?
MAN OF THE MATCH
Glenn Murray (Brighton). Dangerous throughout, scoring a strong brace to give his team an unassailable advantage.
PLAYER RATINGS
West Ham: Hart 4, Zabaleta 5, Reid 5, Fonte 5, Masuaku 6, Obiang 6, Kouyate 6, Antonio 5, Lanzini 6, Arnautovic 5, Chicharito 5. Subs: Adrian, Byram, Ogbonna, Cresswell, Noble, Fernandes 5, Ayew 5.
Brighton: Ryan 7, Bruno 8, Dunk 8, Duffy 7, Bong 7, Knockaert 8, Stephens 7, Propper 7, Izquierdo 8, Gross 7, Murray 8. Subs: Krul, Goldson, March 7, Schelotto 7, Suttner, Brown 7, Molumby.
Brighton's English striker Glenn Murray (C) celebrates with teammates after scoring their third goal from the penalty spot during the English Premier League football match between West Ham United and Brighton and Hove Albion at The London Stadium, in east
Image credit: Getty Images
KEY MOMENTS
10’ GOAL! After a free kick just outside the box, Brighton get the Friday night party started. It's hit in by Gross towards the penalty spot, and that is off Murray's head, past Hart into the net.
45’+2 GOAL! Izquierdo scores a BEAUTIFUL goal. He cuts inside from the right, strikes from the edge of the box, and Hart gets a hand to it, but that's simply not enough.
64' CLOSE! Lanzini curls his free kick wide of the post, but Ryan didn't know that and touched it round for a corner.
75' GOAL! Penalty to Brighton after Zabaleta rugby-tackled Murray, and the Brighton player puts it away himself.
KEY STATISTICS
- This was West Ham's heaviest home league defeat against a newly promoted side since November 1931 (1-5 v West Brom).
- Both of Glenn Murray's braces in the Premier League have been against West Ham (also February 2015 for Crystal Palace).
Stats courtesy of @OptaJoe
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