The Mrs. William B. Astor House was a mansion on the Upper East Side of Manhattan, New York City, at 840-841 Fifth Avenue on the northeast corner of 65th Street, completed in 1896 and demolished around 1926.

John Jacob Astor IV was an American business magnate, real estate developer, investor, writer, lieutenant colonel in the Spanish–American War, and a prominent member of the Astor family. He was among the most prominent American passengers aboard RMS Titanic and perished along with 1,500 people when the ship sank on her maiden voyage. Astor was the richest passenger aboard the RMS Titanic and was thought to be among the richest people in the world at that time, with a net worth of roughly $87 million when he died.