Cavorite is a fictional substance first described in the novel The First Men in the Moon by H.G. Wells. In the book Wells' scientist character Mr Cavor creates and names this fantastic material. Cavorite is a substance which is able to negate the effects of gravity, making objects shielded by cavorite weightless. The protagonists in the novel create a sphere of cavorite in which they travel to the moon. Cavorite is also opaque to heat, light and electric waves.

The idea of a substance impervious to gravity is likely to violate the second law of thermodynamics, since it implies that objects could be moved without using energy. Or the production of cavorite may require an amount of energy which then dissipates as the cavorite is used. The idea has not spread widely in SF, as opposed to the idea of propulsion, as demonstrated in the cannon which shoots travellers to the moon in Jules Verne's earlier work, From the Earth to the Moon. In his opening chapters Wells plays around briefly with the ideas and implications of the substance but he soon casts it aside in order to explore his imagined selenite society inside the moon.

Cavorite also appears in the first collection of the Alan Moore comic book The League of Extraordinary Gentlemen, it is used here as the newest gain in technology which our heroes seek to keep from reaching the hands of evil.