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.

The dress rehearsal is a full-scale rehearsal where the actors and/or musicians perform every detail of the performance. For a theatrical performance, cast members wear their costumes. The actors may use props and backdrops and do not use scripts although the stage manager and director might do so.

For a musical performance, the dress rehearsal does not require wearing formal concert outfits (such as, tuxedos and gowns). In music, the dress rehearsal is the final rehearsal before the performance; initial rehearsals will often involve working on challenging sections of the piece or pieces, but during the dress rehearsal, the piece or pieces are typically played in their entirety.

In theatre, a performing arts ensemble rehearses a work in preparation for performance before an audience. Rehearsals that occur early in the production process are sometimes referred to as "run-throughs". Typically, a run-through does not involve most of the technical aspects of a performance, such as costumes, lights, and sound and is primarily used to assist performers in learning dialogue or music and to solidify aspects of blocking, choreography, and stage movement.

A "cue to cue" or "Q-2-Q" is a type of technical rehearsal and is intended primarily for the lighting and audio technicians involved in a performance although they are of great value to the entire ensemble. It is intended to allow the technicians and stage manager to rehearse the technical aspects of a performance (when lights have to be turned on, sound effects triggered, and items rolled on and off the stage) and to identify and resolve any glitches that might arise. Performers do not typically rehearse entire scenes during a Q-2-Q but instead perform dialogue or actions only that are used by the stage manager as a marker for when to initiate technical sequences or cues (hence the title). Abbreviated Q-2-Qs in which only the opening and closing sequences of each act or scene are performed are sometimes referred to as "tops and tails". It is rare for any but the most technically-complex performances to have Q-2-Q rehearsals other than during technical week.