A stunning strike from Alex Oxlade-Chamberlain was enough to earn Arsenal victory in the Community Shield.
It was the Gunners' first win over Chelsea since 2011, but the game was a lot tighter than that 5-3 thriller.
Also, quite remarkably, it was Arsene Wenger's first victory against Jose Mourinho since the Portuguese arrived in England in 2004.
Chelsea saw early claims for a penalty waved away by referee Anthony Taylor.
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But it was Arsenal who drew first blood with a stunning strike from Alex Oxlade-Chamberlain.
Amazingly it was the first goal the Gunners had scored against Chelsea since Jose Mourinho returned to Stamford Bridge.
Ramires twice went close as Chelsea looked to get back on level terms, but Arsenal went into the break a goal to the good.
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Chelsea made a couple of changes early in the second half, bringing on Radamel Falcao and Oscar, and it brought them a big chance, which was wasted by Eden Hazard.
Petr Cech was not troubled too much by his former team-mate, but he stood firm when called into action.
Chelsea continued to labour in front of goal, and both Santi Cazorla and Kieran Gibbs could have wrapped up victory for Arsenal.
But it wouldn't matter, as Arsene Wenger's team held on to end their Chelsea jinx.
It will surely give Arsenal hope of launching a title charge, despite earlier
claims from Roy Keane that an obsession with selfies was holding them back.
Chelsea will point to the absence of Costa, but we may well be set for a much more competitive title race this season.
