Neptune

 has several meanings pertinent to the Doctor Who universe. They are listed below in alphabetical order by the disambiguation term — that is, the bit between the parentheses in a title like Waitress (Vincent and the Doctor).

In-universe

 * Neptune (Guests of King Neptune) (COMIC: Guests of King Neptune)
 * Neptune (planet), a planet in the Sol system
 * Neptune, Roman name for the god Poseidon (PROSE: Byzantium!)

Behind the scenes

 * Neptune (short story), a short story printed in Short Trips: The Solar System