Planet X is a disproved hypothetical planet proposed in 1906 by Percival Lowell to have existed beyond the planet Neptune.
Planet X may also refer to: Astronomy 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 planet Daffy Duck seeks in the 1953 Merrie Melodies cartoon Duck Dodgers in the 24½th Century The home planet of the Xiliens, a fictional alien race featured in the 1965 kaiju film Invasion of Astro-Monster A planet in David Ossman's 1973 sci-fi comedy album How Time Flys
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 Packages from Planet X, a 2013–14 animated television series created by Jeff Harter and aired on Teletoon Planet X Limited, a British bicycle company Planet X Television, an action sports TV show
See also List of hypothetical Solar System objects Trans-Neptunian object Tenth planet (disambiguation) Ninth planet (disambiguation)