The Groundlings is an American improvisational and sketch comedy troupe and school based in Los Angeles, California. The troupe was formed by Gary Austin in 1974 and uses an improv format influenced by Viola Spolin, whose improv techniques were taught by Del Close and other members of the Second City, located in Chicago and later St. Louis. They used these techniques to produce sketches and improvised scenes. Its name is taken from Shakespeare's Hamlet, Act III, Scene II: "...to split the ears of the groundlings, who for the most part are capable of nothing but inexplicable dumbshows and noise." In 1975 the troupe purchased and moved into its location on Melrose Avenue.

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.