The Triple Palace, also known as the William H. Vanderbilt House, was an elaborate mansion at 640 Fifth Avenue between 51st Street and 52nd Street in Midtown Manhattan, New York City. The urban mansion, completed in 1882 to designs by John B. Snook and Charles B. Atwood, was owned by members of the Vanderbilt family. It was composed of two portions: a single-family unit to the south and a two-family unit to the north. William Henry Vanderbilt owned and lived in the southern portion. Two of his daughters, Emily Thorn Vanderbilt and Margaret Louisa Vanderbilt Shepard, along with their respective families, occupied the two residences in the northern portion.