Mister X
- Afrika Islam
- Aquamania
- Ben Zygier
- Carl Sagan
- Cyclone Mackey
- Dan Marsh
- Die Zirkusprinzessin
- Doctor X (disambiguation)
- Donald Graves (Kremlinologist)
- Enai Noki Paayum Thota
- Fouad el-Mohandes
- Gaston Defferre
- George F. Kennan
- God in Three Persons (album)
- Howdy Doody
- JFK (film)
- Jerry Balisok
- John Doe
- John Mutton (Canadian politician)
- Kung-Fu Master (video game)
- List of Big Time Rush characters
- List of Lupin III characters
- Lysergic Acid Diethylamide (Fringe)
- Mega Man (Archie Comics)
- Mega Man 6
- Miller Barber
- Miss X (disambiguation)
- Mister X (1958 film)
- Mister X (1967 film)
- Mister X (Marvel Comics)
- Mister X (Vortex)
- Mister X (band)
- Mondo Gecko
- Mr. X (1987 film)
- Mr. X (2015 film)
- Mr. X (Amphibia character)
- Mr. X (Amphibia episode)
- Mr. X (Resident Evil)
- Mr. X (Simpsons)
- Mr. X (novel)
- Mr. X in Bombay
- Nomen nescio
- Norman Wexler
- Oniichan no Koto Nanka Zenzen Suki Janain Dakara ne!!
- Pauline Murray And The Invisible Girls
- Professor X (disambiguation)
- Robin Quivers
- Scotland Yard (board game)
- Shaun the Sheep Movie
- Streets of Rage
- The Amazing Mr X (comics)
- The Amazing Mr. X
- The Man Called X
- The Meatmen
- The Ship (video game)
- The X's
- Victor (Alex Lifeson album)
- Vienna (album)
- Wanted (2008 film)
- X (The X-Files)
- X (disambiguation)