Perelandra is the planet ruled by the Green Lady in C.S. Lewis’s novel Perelandra.
Published in 1943, Perelandra is the second book of Lewis’s Ransom Trilogy. Dr. Elwin Ransom travels to the planet Perelandra, which is also identified with Venus, where he encounters the Green Lady and becomes involved in a struggle over obedience, temptation, and the future of the world.
The planet is presented as a young, unfallen world with floating islands and unusual natural conditions. Lewis uses its setting to rework elements of the biblical temptation story while creating a distinct imaginative environment rather than simply retelling Genesis.
Malacandra is the trilogy’s name for Mars and belongs to Out of the Silent Planet. Thulcandra is Lewis’s name for Earth. These invented planetary names are why the answer is easy to mix up with other locations in the trilogy.