Arthur Masuaku came off the bench to deceive Edouard Mendy and secure a 3-2 victory for the Hammers, who had to come from behind on three occasions and stunned the Premier League leaders.
Thiago Silva opened the scoring the visitors with a precise header from a corner which evaded Lukasz Fabianski, but he could do nothing to stop the Hammers from equalising through Manuel Lanzini's penalty.
Yet the Blues roared back into the lead themselves when Mason Mount fired home a spectacular volley just before half time to silence the home crowd.
West Ham have been irrepressible under David Moyes this season and have already beaten Leicester, Tottenham, Manchester City and Manchester United this season for a reason and duly responded.
Jarrod Bowen was a nightmare for the Chelsea defence and got his deserved goal, before Masuaku lashed home a shot past Mendy, which will have fans debating long into the night whether he meant it or not.
The roar from the London Stadium at the full time whistle was just reward for David Moyes' men as they lapped up the adulation, perhaps none more so than tireless midfielder Soucek.
The Czech Republic captain embraced fans in the crowd bearing the flag of his home nation and happily posed for selfies with the jubilant Hammers crowd.
After donating his shirt to a young member of the crowd, the topless 26-year-old proceeded to perform a lap of honour and gave high-fives out to anyone with their arms out.
The result kept West Ham firmly in the hunt for the Champions League places, whilst gifting Liverpool the chance to usurp Chelsea at the top of the table.