Malacandra is the fictional planet in the first book of C.S. Lewis’s Space Trilogy.
Out of the Silent Planet, published in 1938, follows the philologist Elwin Ransom after he is kidnapped and taken into space. The destination is called Malacandra, a planet that humans on Earth identify with Mars. Lewis uses the journey to explore language, colonialism, morality, and humanity’s place in the universe.
The trilogy continues with Perelandra, published in 1943, and That Hideous Strength, published in 1945. Perelandra is the planet associated with Venus, so it is a related setting but not the answer to this question.
Malacandra is often confused with Narnia because both belong to Lewis’s imaginative fiction. They are separate fictional worlds, and the Space Trilogy is aimed more at adult readers than the Narnia books.