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Improvisational theatre — usually shortened to improv — is a form of live theatre in which the scenes, characters and dialogue are invented on the spot, without a script. Players step on stage knowing only a suggestion from the audience (a place, a relationship, a profession, an emotion) and build the story moment by moment. A musician often improvises alongside them.
The work is collaborative: each player accepts what their partner offers and adds to it, so the story emerges from spontaneity and mutual inspiration rather than from a writer's plan. Daily life becomes the stage; the negating intellect gives way to fantasy.
What are the rules of improv?
Almost every improv training in the world teaches three core principles first:
- "Yes, and" — accept your scene partner's offer and build on it instead of negating or blocking.
- Make your partner look good — focus on supporting the other player, not on being clever yourself.
- There are no mistakes — every unexpected move is a gift to be incorporated, not a problem to be fixed.
See the three rules of improv for a deeper treatment, and our warm-up games for exercises that put the rules into practice.
Short form vs. long form
Short-form improv (the Whose Line Is It Anyway? style) is built around discrete games of 2–5 minutes, each with a comedic constraint set by the audience — see our list of improv games.
Long-form improv builds a single 25–60 minute show from one suggestion, weaving multiple scenes into a unified piece. The best-known long form is the Harold, developed at iO Chicago.
History
The roots of modern improvisational theatre run through three traditions.
Commedia dell'Arte (16th–18th century, Italy) — masked actors improvised around stock characters and basic plot scenarios. This was the first organized form of improvised theatre in the Western tradition and laid the groundwork for everything that followed.
Viola Spolin (Chicago, 1940s–50s) — Spolin developed a body of improvisation exercises she called "theater games", originally to help immigrant children learn English through play. Her book Improvisation for the Theater (1963) codified the work, and her games are still the backbone of most improv training today. Her son Paul Sills founded the student drama group The Compass Players in Chicago in 1955, which later evolved into The Second City (1959). Inspired by Bertolt Brecht's theatrical theories, The Compass Players revived the principles of Commedia dell'Arte and performed socio-critical, satirical improvisations from audience-suggested scenarios.
Keith Johnstone (UK and Canada, 1960s onward) — working at London's Royal Court Theatre, Johnstone experimented with what he called the "Theatre Machine". Because British censorship at the time required scripts to be approved before performance, he framed his improvised work as a sporting event and called it Theatresport. He later emigrated to Canada and founded the still-active Loose Moose Theatre Company. His book Impro (1979) reshaped how improvisers think about spontaneity, narrative and status.
These streams converged into today's global improv scene. The competitive two-team format Johnstone developed in Canada also took root in France, Spain and Italy, while the Chicago tradition spread across North America and into Europe through workshops and festivals.
Earlier traces of improvised performance go much further back — to the mimus of ancient Greece, to medieval troubadours, and to the Stegreiftheater experiments of early-20th-century Vienna, which Jakob Levy Moreno later developed into psychodramatic role-playing with therapeutic aims. None of these connect directly to the modern Chicago and European lineages, but they show that improvisation has been part of theatre for as long as theatre has existed — receding when scripted drama dominated, and resurfacing in the 20th century as an art form in its own right.
Is improv just comedy?
Most public improv shows are comedic, but improv is not by definition comedy. The technique is the absence of a script — comedy is a frequent outcome but not a requirement. Improvisation is also used in dramatic theatre, in actor training, in therapy (psychodrama), and in corporate education.
Getting started
Curious to try improv yourself? Most cities have drop-in classes; check our improv group directory to find a troupe or school near you, or browse our calendar of workshops and shows. For ideas to play at home, start with our list of improv games and warm-ups.