The Muny, short for The Municipal Theatre Association of St. Louis, is an outdoor musical amphitheatre, located in Forest Park, St. Louis, Missouri. The theater seats 11,000 people with approximately 1,500 free seats in the last nine rows that are available on a first come, first served basis. The Muny has completed its 92nd annual summer season. The Muny seasons run every year from mid-June to mid-August. It is run by a not-for-profit organization. The current president and chief executive is Dennis M. Reagan. The current executive producer is Mike Isaacson.

In 1914, Luther Ely Smith began staging pageant-Masques on Art Hill in Forest Park. In 1916, a grassy area between two oak trees on the present site of The Muny was chosen for a production of As You Like It produced by Margaret Anglin and starring Sydney Greenstreet with a local cast of "1,000 St. Louis folk dancers and folk singers."

Soon after, the Convention Board of the St. Louis Advertising Club was looking for an entertainment feature for its thirteenth annual convention, which was to take place June 3, 1917. Mayor Henry Kiel, attorney Guy Golterman, and Parks Commissioner Nelson Cunliff stepped in and, in forty-nine days (not counting seven lost to rain), created the first municipally owned outdoor theatre in the United States. On June 5, 1917, the opera Aida was presented on what would become the Muny stage.