What is the subtitle of Prince Caspian in its full title?

The subtitle of Prince Caspian in its full title is The Return to Narnia.

C. S. Lewis’s novel was originally published in 1951 as Prince Caspian: The Return to Narnia. It is the second-published book in The Chronicles of Narnia, following The Lion, the Witch and the Wardrobe, although many modern editions place it fourth in Narnia’s internal chronology.

The title describes the Pevensie children’s second visit to Narnia. Only about a year has passed in England, but roughly 1,300 years have passed in Narnia. Their former kingdom has fallen into ruin, and the Telmarines now dominate the land under King Miraz.

A common mix-up is confusing the subtitle with invented alternatives such as The Heir of Narnia or The King of Narnia. The story does involve Caspian’s claim to the throne, but those phrases are not part of the book’s canonical title.