Felix Baumgartner jumped from a helium balloon in the stratosphere to become the first person to break the sound barrier without vehicular power.

Felix Baumgartner was an Austrian skydiver, extreme sportsman, and BASE jumper. He was widely known for jumping to Earth from a helium balloon in the stratosphere on 14 October 2012 and landing in New Mexico, United States, as part of the Red Bull Stratos project. By doing so, he set world records for skydiving an estimated 39 km (24 mi), reaching an estimated top speed of 1,357.64 km/h (843.6 mph), or Mach 1.25. He became the first person to break the sound barrier relative to the surface without vehicular power on his descent. He broke skydiving records for exit altitude, vertical freefall distance without a drogue parachute, and vertical speed without a drogue. Although his name is still attached to the two last records, his exit altitude record was broken two years later, when on 24 October 2014, Alan Eustace jumped from 135,890 feet with a drogue.

Red Bull Stratos was a high-altitude skydiving project involving Austrian skydiver Felix Baumgartner. On 14 October 2012, Baumgartner flew approximately 39 kilometres (24 mi) into the stratosphere over New Mexico, United States, in a helium balloon before free falling in a pressure suit and then parachuting to Earth. The total jump, from leaving the capsule to landing on the ground, lasted approximately ten minutes. While the free fall was initially expected to last between five and six minutes, Baumgartner deployed his parachute after 4 minutes and 19 seconds.

The stratosphere is the second-lowest layer of the atmosphere of Earth, located above the troposphere and below the mesosphere. The stratosphere is composed of stratified temperature zones, with the warmer layers of air located higher and the cooler layers lower. The increase of temperature with altitude is a result of the absorption of the Sun's ultraviolet (UV) radiation by the ozone layer, where ozone is exothermically photolyzed into oxygen in a cyclical fashion. This temperature inversion is in contrast to the troposphere, where temperature decreases with altitude, and between the troposphere and stratosphere is the tropopause border that demarcates the beginning of the temperature inversion.