A rehearsal is an activity in the performing arts that occurs as preparation for a performance in music, theatre, dance and related arts, such as opera, musical theatre and film production. It is undertaken as a form of practising, to ensure that all details of the subsequent performance are adequately prepared and coordinated. The term rehearsal typically refers to ensemble activities undertaken by a group of people. For example, when a musician is preparing a piano concerto in their music studio, this is called practising, but when they practice it with an orchestra, this is called a rehearsal. The music rehearsal takes place in a music rehearsal space.

A rehearsal may involve as few as two people, as with a small play for two actors, an art song by a singer and pianist or a folk duo of a singer and guitarist. On the other end of the spectrum, a rehearsal can be held for a very large orchestra with over 100 performers and a choir. A rehearsal can involve only performers of one type, as in an a cappella choir show, in which a group of singers perform without instrumental accompaniment or a play involving only theatre actors; it can involve performers of different instruments, as with an orchestra, rock band or jazz "big band"; vocal and instrumental performers, as with opera and choral works accompanied by orchestra; or a mix of actors, vocalists, instrumentalists and dancers, as with musical theatre.

Rehearsals of small groups, such as small rock bands, jazz quartets or organ trios may be held without a leader; in these cases, the performers jointly determine how to run the rehearsal, which songs to practice, and so on. Some small groups may have their rehearsals led by a bandleader. Almost all mid- to large-group performances have a person who leads the rehearsals; this person may be a bandleader in a rock, country, or jazz setting; conductor in classical music (including opera); director in theatre or musical theatre; or film director for movies.

While the term is most commonly used in the performing arts to refer to preparation for a public presentation, the term is also used to refer to the preparation for other anticipated activities, such as wedding guests and couples practicing a wedding ceremony, paramedics practicing responding to a simulated emergency, or troops practicing for an attack using a mock-up of the building.