Hearing, or audition, is one of the traditional five senses and refers to the ability to detect sound.

In human beings, hearing is performed by the ears, which also perform the function of balance, a sense in itself but not one of the traditional list (due to Aristotle). This is in common with most mammals. Many other organisms also have some form of hearing, either by some sort of ear, or by other structures, or by a combination.

A common rule of thumb used to describe human hearing is that human hearing is sensitive in the range of frequency of 20 Hz to 20 kHz, though this varies significantly with age, occupational hearing damage, and gender; some individuals are able to hear up to 22 kHz and perhaps beyond, while others are limited to about 16 kHz. Frequencies capable of being heard by humans are called audio or referred to as sonic. Frequencies higher than audio are referred to as ultrasonic, while frequencies below audio are referred to as infrasonic.