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 theater, which seats 299, and the Downstairs theater, 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.