BASE jumping, is an activity that employs a parachute or the sequenced use of a wingsuit and parachute to jump from fixed objects, with the parachute unopened at the jump. “BASE” is an acronym that stands for the four categories of fixed objects from which one can jump:

• Building
• Antenna
• Span
• Earth

The acronym “BASE” was made up by film-maker Carl Boenish, his wife Jean Boenish, Phil Smith, and Phil Mayfield. Carl was the real catalyst behind modern BASE jumping, and in 1978 filmed the first BASE jumps to be made using ram-air parachutes and the freefall tracking technique (from El Capitan, in Yosemite National Park). While BASE jumps had been made prior to that time, the El Capitan activity was the effective birth of what is now called BASE jumping. BASE jumping is significantly more dangerous than similar sports such as skydiving from aircraft, and is currently regarded by many as a fringe extreme sport or stunt.

BASE numbers are awarded to those who have made at least one jump from each of the four categories.

During the early eighties, nearly all BASE jumps were made using standard skydiving equipment, including two parachutes (main and reserve), and deployment components. Later on, specialized equipment and techniques were developed that were designed specifically for the unique needs of BASE jumping.