Jules Ephraim Mastbaum (July 7, 1872 – December 8, 1926) was a Philadelphia movie theater magnate and philanthropist.

He donated the Rodin Museum and its collection to the city of Philadelphia.

[1] Mastbaum began investing in real estate by purchasing Felix Isman's portfolio with his brother Stanley and Alfred W. Fleisher as partners forming the firm Mastbaum Brothers and Fleisher.

[1] He opened the first nickelodeon in Philadelphia at an empty storefront at 8th and Market and he then went on to purchase the Regent Theatre in 1911.

[1] After his death in 1926, his wife assumed control of Stanley Company of America.