The Upton Sinclair House, located at 464 N. Myrtle Avenue, Monrovia, California, was the home of American novelist Upton Sinclair between 1942 and 1966. It is a 1923 Neo-Mediterranean building in a district of similar houses, located in the suburban Los Angeles community of Monrovia, in the San Gabriel Valley. Most of his later works were written while he lived here. He had converted the rear garage into his study. The grounds also include a concrete vault where he kept all his papers.
The house was designed by California architect Frederick H. Wallis and is privately owned. It is made of poured concrete and includes "ball-and-ribbon" concrete moldings and Batchelder tile.