The Gunners impressive 14-game unbeaten streak against West Ham ended abruptly thanks to super signing Petr Cech putting in a super stinker of a performance at the Emirates.
Goals in either half from Cheik Kouyate and Mauro Zarate helped the Hammers dealt an early blow to Arsenal's title hopes and ensured the 200th and 150th Premier League appearances for Laurent Koscielny and Santi Cazorla could not be commemorated with a victory.
Arsene Wenger's men were overwhelming favourites to win the game given their superiority over their East London rivals, the fact they had a brilliant pre-season winning three trophies and because they lost mid-week in the Europa League.
However, Slaven Bilic's men showed no sign of tiredness as they took the lead on the stroke of half-time. Former Marseille man Payet put in a free-kick in a troubling area leading to Cech making the first of his two mistakes as he came out of position, allowing Kouyate an easy header.
The Hammers could have gone ahead beforehand as Diafra Sakho gave the entire defence the runaround but failed to notice 16-year-old Reece Oxford was free in the area and potentially had a chance to net on his senior debut for the club. Nonetheless, Oxford who is now West Ham's youngest ever player, will be delighted with how he played as he had the best passing percentage out of anyone (95%).
Alex Oxlade-Chamberlain will also have to take blame for the goal as his casual approach on the ball led to him being dispossessed near his own penalty area.
Prior to this match Olivier Giroud had scored five in five against West Ham and was picked ahead of Theo Walcott as the two strikers engage in battle for the sole striking spot. However, the Frenchman, as is often the case failed to deliver when it really mattered. His performance was summed up moments before Zarate's goal when he had a clear shot at goal, dithered and allowed the opposition to close him down. Although he still managed to get a shot in, it was off target until it was deflected harmlessly into Adrian's arms.
Walcott, as well as Alexis Sanchez both came on after the second goal but had no tangible effect on the game. The defeat is Arsenal's first opening day defeat since losing 3-1 to Aston Villa three years ago.