The 56-year-old lost his life while flying a motor-powered paraglider in Porto Sant'Elpidio, Italy, at around 4pm.
The Austrian set records for skydiving an estimated 24 miles and reaching an estimated top speed of Mach 1.25 (843.6mph), becoming the first person ever to break the sound barrier without vehicular support.
It has been speculated by Italian media that he suffered a cardiac arrest mid-air during his final trip.
He was said to be feeling unwell prior to take off before losing control of his craft and then crashing to the ground.
But by the time emergency responders arrived on the scene to help him, he was already in cardiac arrest, according to Repubblica.
They requested an air ambulance for transport to the hospital, but he was pronounced dead at the scene.
His wife, Mihaela Schwartzenberg, who was also in the area on a couple's holiday, was informed and immediately rushed to the scene.
Reports also revealed a hotel employee was struck by Baumgartner at the end of his descent.