James Thorne Smith Jr. (March 27, 1892-June 21, 1934), was an American writer of humorous supernatural fantasy fiction.

Best known today for his creation of Topper, Smith's comic fantasy fiction (most of it involving sex, lots of drinking, and supernatural transformations, and aided by racy illustrations) sold millions of copies in the early 1930s. Smith drank as steadily as his characters; his appearance in James Thurber's The Years With Ross involves an unexplained week-long disappearance. Smith was born in Annapolis, Maryland the son of a Navy commodore, attended Dartmouth College, and after hungry years in Greenwich Village working part-time as an advertising agent, Smith achieved meteoric success with the publication of Topper in 1926. He died of a heart attack while vacationing in Florida.