ComedySportz (CSz) is an improvisational comedy organization started in 1984 in Milwaukee, Wisconsin, by a group of local comedians including Dick Chudnow, Bob Orvis, Brian Green, and others.

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.