Mongo is a rogue planet that travels through our solar system under the control of its dictator, Ming the Merciless. Mongo is an inhospitable planet, with various extreme climate zones. Travelers to Mongo must pass through a "Death Zone" on the way, described by scientist Dr. Hans Zarkov as being "a zone devoid of any force". ("Chapter 101: The Planet of Peril")
Mongo has at least 2 moons, one of them being the planetoid Lunita.
The area around Ming's palace is desolate and devoid of vegetation. Dragons live in the nearby caves. Other vicious animals of Mongo include Monkey Men, orangopoid, and white-striped, bear-like animals.
The people of Mongo have progressed scientifically beyond Earth. According to Ming, "the reason for our success is that we possess none of the human traits of kindness, mercy, or pity! We are coldly scientific and ruthless!" ("Flash Gordon (comic strip)")
They use a lunar calender as several characters use the phrases "new moon" or "third moon".
A description of the fictional planet Mongo states: "Mongo is approximately one of the diameter of earth but has a gravitational density that is only slightly less. It is a relatively young world with towering mountains not yet worn smooth by time and many areas of volcanic activity. Its vegetation is still limited to isolated areas of botanical giants. Biologically it is still in the era of reptilian giants. Man evolved fast into diverse races, many of which possess amazingly advanced technology while others still live in primitive and unexplored regions.":
- Arboria: a forest principality ruled by Prince Barin.
- Coralia: an underwater kingdom beneath the Sea of Mystery. It is located east of Arboria and is ruled by Queen Undina.
- Frigia: a frozen kingdom ruled by Queen Fria.
- Volcania: the Fire Lands are located on the east coast of Tropica, and is home of Gundar, the Desert Hawk.
- The Land of the Lion Men also borders the Sea of Mystery, and is ruled by King Jugrid and Prince Thun.
- The Lost Continent: a largely unexplored island continent between Flame World and Tropica.
- The Magnetic Mountains are located east of the Land of the Lion Men and is a base of operations for Ming the Merciless.
- The Sky City of the Hawk Men is located north of the Magnetic Mountains, the ruler is King Vultan.
- Tropica is a continent of forests. It is directly east of the Sky City. Queen Desira rules Tropica.
- Comprehensive List of Planets in Science Fiction
- Map of the Planet Mongo
- Flash Gordon’s planet Mongo