外外百老汇音乐剧（Off Off Broadway，或译「超外百老汇」、「第三戏剧(界)」、「前卫戏剧」）。外外百老汇音乐剧有相当多实验戏剧的形式，也最便宜，如果票房很好，就会被移到外百老汇加强宣传，而只有受到大众欢迎、票房非常好的才会在内百老汇上演。在地理上来说，在纽约百老汇大街上，44街至53街之间的剧院称为内百老汇（也就是百老汇），而百老汇大街41街和56街上的剧院则称为外百老汇。 一般来说，超外百老汇的座位少于100个。而所谓的超外百老汇运动（Off-Off-Broadway movement）则开始于1958年，它主要的精神在于全盘地拒绝商业性的剧场演出。

Off-Off-Broadway theatrical productions in New York City are those in theatres that are smaller than Broadway and Off-Broadway theatres. Off-Off-Broadway theatres are usually theatres that have fewer than 100 seats, though the term can be used for any show in the New York City area that employs union actors but is not under an Off-Broadway, Broadway, or League of Resident Theatres contract. It is often used as a term relating to any show with non-union actors. The shows range from professional productions by established artists to small amateur performances.