Look up Planet X in Wiktionary, the free dictionary.

Planet X may refer to:

Astronomy

• Planet X, a disproved hypothetical planet proposed in 1906 by Percival Lowell to have existed beyond the planet Neptune.
  • Colloquially, and by extension, any hypothetical trans-Neptunian planet, in particular Planet Nine.

Science fiction

• Planet X, the home planet of Marvel Comics character Groot and other flora colossi
• "Planet X" (comics), a 2004 X-Men comic book story-line
• Planet X (Star Trek), a 1998 novel depicting a crossover between The X-Men and Star Trek
• The name for several Fictional planets of the Solar System
• The name for several fictional extrasolar planets
• A planet in David Ossman's 1973 sci-fi comedy album How Time Flys
• The planet Daffy Duck seeks in the cartoon Duck Dodgers in the 24½th Century.

Music

• Planet X (Derek Sherinian album), 1999
• Planet X (Helios Creed album), 1994
• Planet-X, an album by bassist Jimmy Johnson
• Planet X (band), a progressive metal band founded by Derek Sherinian
• Plan-It-X Records, a DIY punk rocks record label

Other uses

• Nibiru cataclysm, a supposed impending disastrous encounter between Earth and a large astronomical object
• Operation Planet X, a military operation during the Iraq War in 2003
• Planet X Limited, a British bicycle company
• Planet X Television, an action sports TV show