The Mrs. O. H. P. Belmont House was a mansion located at 477 Madison Avenue on the northeast corner of 51st Street in Midtown Manhattan, New York City, New York, United States.

The neoclassical three-story townhouse had a limestone facade and interior rooms in an eclectic mix of styles.

Construction was still underway when Oliver Belmont died, and Alva announced that she would build an addition that was an exact reproduction of the Gothic Room in Belcourt Castle, to house her late husband's collection of medieval and early Renaissance armor.

[1][2] The mansion was then used by the Catholic Charities of the Archdiocese of New York until the church sold it in 1951.

The site is now occupied by a 23-story office tower designed by Kahn & Jacobs, constructed between 1952 and 1953.