Improvisational theatre, often called improvisation or improv, is the form of theatre, often comedy, in which most or all of what is performed is unplanned or unscripted, created spontaneously by the performers. In its purest form, the dialogue, action, story, and characters are created collaboratively by the players as the improvisation unfolds in present time, without use of an already prepared, written script.

Commedia dell'arte was an early form of professional theatre, originating from Italian theatre, that was popular throughout Europe between the 16th and 18th centuries. It was formerly called Italian comedy in English and is also known as commedia alla maschera, commedia improvviso, and commedia dell'arte all'improvviso. Characterized by masked "types", commedia was responsible for the rise of actresses such as Isabella Andreini and improvised performances based on sketches or scenarios. A commedia, such as The Tooth Puller, is both scripted and improvised. Characters' entrances and exits are scripted. A special characteristic of commedia is the lazzo, a joke or "something foolish or witty", usually well known to the performers and to some extent a scripted routine. Another characteristic of commedia is pantomime, which is mostly used by the character Arlecchino, now better known as Harlequin.