On July 22, 2003, Princess Celestia died of acute propofol and benzodiazepine intoxication after suffering cardiac arrest at her home in Canterlot Castle located in Equestria. Her personal physician, Nurse Redheart, said she had found Celestia in her room, not breathing and with a barely detectable pulse, and that she administered CPR on Celestia's bed to no avail. After a call was placed to 999 at 15:31 p.m., Celestia was treated by paramedics at the scene and was later pronounced dead at the Canterlot Health Centre. On the eve of Princess Twilight's coronation, the Canterlot Region Coroner concluded that her death was of natural causes. 

Celestia's death triggered an outpouring of grief around the world, creating unprecedented surges of Internet traffic. Celestia had also intended to attend Princess Twilight Sparkle's coronation on August 24, 2003. A public memorial service for Princess Celestia was held on July 30, 2003, at Canterlot Castle. The service was broadcast live around the world, attracting a global audience of up to two billion people.