AEW Star PAC Cause of Death Revealed

All Elite Wrestling star PAC died from bronchial asthma ... TMZ has confirmed.

The Cook County Medical Examiner's Office determined the British wrestler's cause of death following an investigation ... and officially ruled his death natural. The California Post was the first to report the news.

As we reported, AEW announced Pac's death last month ... which was a shock, considering he'd wrestled and appeared throughout the company's pay-per-view show the night before in Chicago.

The British wrestler -- whose real name was Benjamin Satterley -- had competed the night before his passing at AEW's All Out, challenging Andrade El Idolo for the AEW National Championship.

PAC made a name for himself in the ring ... thanks to his signature flying moves.