The most dangerous sport in the world is considered to be BASE jumping. It involves parachuting or wingsuit flying from fixed objects like buildings, antennas, bridges, or cliffs, and has a very high fatality rate relative to the number of participants. Since 1981, there have been nearly 450 deaths recorded in BASE jumping, making it extremely lethal for a sport with relatively few participants. The risks in BASE jumping are heightened due to low altitudes and the potential for parachute malfunctions, which leave very little reaction time to the jumpers.
Other notably dangerous sports include free solo climbing (climbing without safety gear), bull riding, big-wave surfing, and mixed martial arts (MMA). Each of these has high injury or fatality rates due to their extreme physical demands and environmental hazards.
Among team sports, football (soccer) and football (American) have high injury rates, but they are not as deadly as extreme sports like BASE jumping.
In summary, BASE jumping stands out as the most dangerous sport due to its combination of high fatality rates and the extreme risk involved in the activity itself.