Planet X

 has several meanings pertinent to the Doctor Who universe and the real world. They are listed below in alphabetical order by surname. If no surname is available, alphabetisation occurs by the disambiguation term — that is, the bit between the parentheses in a title like Waitress (Random Shoes).

In-universe
Planet X (Risk Assessment) - A planet mentioned in the Torchwood novel, Risk Assessment (novel) Planet X (Planet X) - The planet featured in the Bernice Summerfield audio, Planet X (audio story) Planet X (Famine on Planet X) - The planet featured in the Doctor Who annual short story Famine on Planet X (short story)

Real World
Planet X (audio story) - the second story in The Unbound Universe (audio anthology)