West Ham fans had been waiting all season for a performance like this. Now Sam Allardyce and his players must prove it has not come too late as far as automatic promotion is concerned.
Ricardo Vaz Te scored three of the six, with Kevin Nolan and Henri Lansbury the other scorers on a day when Brighton also contributed an own goal.
This was West Ham's first home win since 4 February, a seven-game run that allowed Reading to march past them all the way to the Championship summit. Southampton have also been left in the Royals' wake but this result, coupled with Reading's Friday night success at St Mary's, means West Ham are three points behind Saints with three games to play.
"It was overdue," Allardyce said. "We needed three points and to win them in such style was thrilling and gives us a bit more belief we can do what we wanted to at the start of the season."
The Hammers were on top from the off, Lansbury, the on-loan Arsenal midfielder, striking the crossbar after 40 seconds. The reprieve was short-lived for Brighton as Vaz Te, having received the ball from Nolan, cut inside from the left and saw his effort from 25 yards swerve through the hands of Peter Brezovan. Brezovan was picking the ball out of the net again in the eighth minute when Vaz Te's head was on the end of Gary O'Neil's delivery to the back post.
Nolan made it 3-0 from close range – he almost put it over – when James Tomkins had won a grappling duel with a defender to head Matt Taylor's free-kick across goal.
West Ham relaxed after that as Brighton passed it around without effect for 20 minutes, although Robert Green had to paw a header from Gordon Greer round the post before the break. Vaz Te got his hat-trick with an overhead kick after Marcos Painter failed to head clear. The January signing from Barnsley has now scored nine in seven games.
The fifth was a freak as Carlton Cole's shot, which was going wide, flicked off Lansbury's boot and in. Gary Dicker will not want reminding of the sixth. He missed his kick attempting to clear and felt the ball ricochet off his standing leg and into the net.
"I said a few months ago we were not ready," Gus Poyet said as Brighton's play-off hopes dimmed. "I know what to change for next season."
West Ham (4-4-2): Green; Demel (Collins, 68), Reid, Tomkins, Taylor; O'Neil (Collison, 55), Lansbury, Noble, Nolan; Cole, Vaz Te (Carew, 77).
Brighton (4-3-2-1): Brezovan; Calderon, El-Abd, Greer, Painter; Navarro, Bridcutt, Dicker; Vicente (Noone, 63), Assulin (Mackail-Smith, 53); Barnes (LuaLua, 53).
Referee Roger East.
Man of the match Vaz Te (West Ham).
Match rating 7/10.