Lloyd Cassel Douglas (August 27, 1877 – February 13, 1951) was an American minister and author. Douglas was one of the most popular American authors of his time, although he did not write his first novel until he was 50.

His first novel, Magnificent Obsession, published in 1929, was an immediate success. Critics held that his type of fiction was in the tradition of the great religious writings of an earlier generation, such as Ben-Hur and Quo Vadis. Magnificent Obsession was adapted for the screen twice, first in 1935 in a film starring Robert Taylor and Irene Dunne, and in 1954, with Rock Hudson and Jane Wyman.Douglas then wrote Forgive Us Our Trespasses; Precious Jeopardy; Green Light; White Banners; Disputed Passage; Invitation To Live; Doctor Hudson's Secret Journal; The Robe, and The Big Fisherman, In 1937, Green Light was made into a film starring Errol Flynn. White Banners, starring Claude Raines and Fay Bainter, came to the screen in 1938. The film of Disputed Passage was released in 1939. Dr. Hudson's Secret Journal , a prequel to The Magnificent Obsession, aired on syndicated television in 1955-1957. John Howard starred as Dr. Wayne Hudson in 78 episodes.

The Robe sold more than 2 million copies, without any reprint edition. Douglas sold the motion picture rights to The Robe, though the film, starring Richard Burton, was not released until 1953, after Douglas's death. His own unhappy experience of filming prompted Douglas, when he produced The Big Fisherman as the sequel to The Robe, to stipulate that The Big Fisherman would be his last novel and that he would not permit it to be made into a motion picture, used over the radio, condensed, or serialized. Eventually, The Big Fisherman was filmed in 1959, starring Howard Keel in one of his few non-singing screen roles as Peter. His last book was the autobiographical Time To Remember which described his life up to his childhood and education for the ministry. He died before he was able to write the intended second volume, but the task was completed in The Shape of Sunday by his daughters, Virginia Douglas Dawson and Betty Douglas Wilson. Douglas died in Los Angeles, California. He is buried in Forest Lawn Memorial Park Cemetery in Glendale, California.