Kellertheater Frankfurt, Underground theater in Frankfurt, Germany.

Kellertheater Frankfurt is a theater located in a basement space on Mainstraße in central Frankfurt. The venue operates smaller to mid-size theatrical productions under the management of Junge Bühne Frankfurt e.V.

The theater was founded in 1957 and established itself as a venue for local artists. Over the decades it developed into an important cultural space for theatrical productions in Frankfurt.

The name comes from the vaulted cellar on Mainstraße that the troupe moved into in 1980, previously the rooms of the music venue Sinkkasten. The company is run entirely by volunteers of the Junge Bühne Frankfurt e.V., and non-members of any age can take part on and behind the stage. Once a month the Maleen Studiobühne presents an evening mixing acting, music, literature and multimedia.

The venue is an old vaulted cellar at Mainstraße 2, reached by stairs, so it is not wheelchair accessible. Performances are regularly scheduled on Fridays and Saturdays; the Maleen Studiobühne opens once a month.

The venue's name comes from its home since 1980: a vaulted cellar on Mainstraße that previously housed the music bar Sinkkasten. Before that, the troupe performed in a former cinema in the Nordwestzentrum shopping centre, where few spectators followed. Some Frankfurt professional actors made their first stage appearances here.