Big Planet is the setting for a pair of science fiction novels by Jack Vance, and also the title of the first of the two novels.

The first novel, Big Planet (serialized 1952; published in book form 1957 as an Ace double novel along with Vance's Slaves of the Klau) deals with an immense but metal poor (and so relatively light) planet which had been colonized hundreds of years earlier by misfits, faddists, cultists and anti-government types from Earth. Big Planet has devolved into a huge number of technologically backward societies, many of them ruled by petty tyrants and prey to internecine warfare. Investigators from Earth, headed by protagonist Claude Glystra, arrive to put things right -- to stop the importation of arms and halt Big Planet's slave trade -- only to crash near the territory of Charley Lyssider (the Bajarnum of Beaujolais), one of the worst tyrants. The Earth team attempts to flee to the only safe spot on Big Planet, Earth Enclave, forty thousand miles around the planet. Already at odds with each other, the dwindling team begins to revert to the social level of the rest of Big Planet as the local tyrant tries to pick them off.

The theme of a vast planet riven into a large number of eccentric human societies can be taken as a dry run for Vance's greatest astrogeographic conception--the Gaean Reach composed of thousands of human settled planets with cultures as eccentric as those of Big Planet.

The second novel, Showboat World (1975), also takes place on Big Planet (which is now depicted as an isolated planet within or near the Gaean Reach), but with a different cast of characters. Showboat World tells the adventures of Apollon Zamp, travelling up the river Vissel through a vast territory in order to enter a showboat contest hosted by the king of Soyvanesse. In part, the interest of the story lies in the many different cultures and customs that Zamp encounters on the way to his destination.

The two novels are very different. Big Planet is a conventional space opera, although its setting is one of grandeur and originality. Especially memorable is the scene when Glystra awakens, after the crash of his ship, to the jewel-bright morning light of the quaint village Jubilith on a flowery mountain slope--with a view "vast beyond Earthly conception."

Among the many societies benign or psychopathic that Glystra and his companions encounter along the wind-driven monoline (their version of the Yellow Brick Road), is a utopian society, as opposed to the dystopias that science fiction more often specializes in. The ideal society of Kirstendale appears to be based on snobbish principles, but with an odd twist that reveals it to be surprisingly egalitarian.

Showboat World largely transcends space opera -- it is a skillfully executed farce in which Zamp and another showboat owner continuously try to outwit each other, with both ending up fugitives. At least one scene was influenced by the Royal Nonesuch acting troupe episode in Huckleberry Finn, while Showboat World itself has strongly influenced The Wizard of Karres (2004) by Mercedes Lackey, Eric Flint and Dave Freer. Where the planet itself is the most interesting "character" in Big Planet, it recedes into the background in Showboat World, which focuses on the rascality of its two protagonists and the eccentric nature of the various local villages, towns and baronies they encounter along the river bank.

In a summary of the geography of Big Planet at the beginning of Showboat World, Vance attempts a better explanation than metal-poorness to explain why a planet the size of a gas giant has Earth-style gravity. His effort, although elegant, is even less convincing than his tongue-in-cheek explanation of the Jarnell Intersplit (faster than light) engine in the Demon Prince series. But Vance has never claimed to be a writer of "hard" science fiction.

In Big Planet reference is made to the "one-man planets", slave societies beyond the law owned by wealthy sadists who spend part of their time on Earth, where their nefarious activities outside the civilized galaxy are unknown, and part of their time tormenting their slave planet inhabitants (many of whom were kidnapped from Big Planet). Arguably we see here the first germ of Vance's "Beyond" and the Demon Princes who lurk therein.