What is the name of C.S. Lewis’s science-fiction trilogy about Ransom?

C.S. Lewis’s science-fiction trilogy about Ransom is The Space Trilogy.

The trilogy consists of Out of the Silent Planet, Perelandra, and That Hideous Strength. Its recurring protagonist is Elwin Ransom, a philologist who becomes involved in conflicts extending from Earth to other worlds and, ultimately, into a struggle over the direction of human civilization.

Out of the Silent Planet, published in 1938, sends Ransom to Mars, called Malacandra in the novel. Perelandra, published in 1943, places him on a version of Venus. That Hideous Strength, published in 1945, returns the action to Earth and presents a dystopian conflict involving a modern institution and supernatural forces.

The books combine planetary adventure with theology, language, mythology, and criticism of dehumanizing science. The trilogy is also called the Ransom Trilogy, but The Space Trilogy is its standard collective title.