James Bass Mullinger (1834 or 1843 – 22 November 1917), sometimes known by his pen name Theodorus, was a British author, historian, lecturer and scholar. A longtime university librarian and lecturer at St. John's College, Cambridge, Mullinger was the author of several books detailing the college's history and similar academic subjects. He was also a contributor to many periodicals of the Victorian era, most especially, Cambridge History of Modern Literature, the Dictionary of National Biography and Encyclopædia Britannica.