The Westside Theatre is an off-Broadway performance space at 407 West 43rd Street between Ninth and Tenth Avenues in the Hell's Kitchen neighborhood of Manhattan, New York City. The building houses two auditoriums: the Upstairs Theatre, which seats 270, and the Downstairs Theatre, which features a thrust stage and has a seating capacity of 249. Formerly known as the Chelsea Theatre Center and the Westside Arts Theatre, the building was renovated in 1991.
The Romanesque Revival style building, designed by Henry Franklin Kilburn, was constructed in 1890 for the Second German Baptist Church, which it housed until the 1960s. The site was then occupied by various nightclubs until its establishment as a theatre in 1976.