A bell (old Saxon: bellan, to bawl or bellow) is a simple sound-making device. The bell is a percussion instrument and an idiophone. Its form is usually a hollow, cup-shaped acoustic resonator, which vibrates upon being struck. The striking implement can be a tongue suspended within the bell, known as a clapper, a separate mallet or hammer, or in small bells a small loose sphere enclosed within the body of the bell.

Bells are usually made of cast metal, but small bells can also be made from ceramic or glass. Bells range in size from tiny dress accessories to church bells 5 meters tall, weighing many tons. Historically, bells were associated with religious rituals, and before mass communication were widely used to call communities together for both religious and secular events. Later bells were made to commemorate important events or people and have been associated with the concepts of peace and freedom. The study of bells is called campanology.

A set of bells, hung in a circle for change ringing, is known as a ring of bells or peal of bells.

A set 23 of bells spanning at least two octaves is a carillon.