The Mutual Reserve Building, also known as the Langdon Building and 305 Broadway, is an office building at Broadway and Duane Street in the Tribeca neighborhood of Manhattan in New York City. The 13-story building, constructed between 1892 and 1894, was designed by William H. Hume and built by Richard Deeves, with Frederick H. Kindl as chief structural engineer. It is just east of the Civic Center of Manhattan, and carries the addresses 305–309 Broadway and 91–99 Duane Street.