a branch of the New Theatre movement of the 1960s that aimed to heighten audience awareness of theatre by eliminating the distinction between the audience's and the actors' space. Richard Schechner's environmental productions Dionysus in 69, Makbeth, and Commune were performed in his Performing Garage on Off-Off-Broadway in New York City.

Schechner and the Performance Group (founded 1968) shaped the theatre to conform to each play, constructing different audience frameworks for each production. The sets were usually based on multilevel platforms, balconies, ramps, and scaffolds surrounding a stage that encroached on the audience's territory, providing a wider range of space for the actors and a greater flexibility of interaction between the audience and performers. The audience of the environmental theatre was invited, even expected, to participate. The minimum involvement for the production of Commune, for example, was the audience's removal of its shoes upon entering the garage. To enhance the immediacy of experience the multiple-focus theatre replaced the traditional single focus, allowing more than one scene to be staged at the same time. Schechner's theatrical experiments, inherited from the Polish director Jerzy Grotowski (Grotowski, Jerzy), included the use of psychophysical conditioning exercises for actors, the “collaging” of texts, and the shaping of theatre space.

The concept of environmental theatre was taken to greater extremes by radical American artistic groups such as Welfare State International and the Bread and Puppet Theater. Both took art to the streets, often working in derelict urban neighbourhoods in the latter half of the 20th century and at the beginning of the 21st. Numerous other experimental companies defied the traditional boundaries of audience-actor relationships, especially in nontheatre venues.