Geofiction is a hobby where one or more people design imaginary cities, countries and even entire worlds. This includes placenames, culture, political structure and even constructed languages (conlangs). Geofiction is a type of world-building.

Geofiction can encompass everything from diagrams of imaginary streets drawn by a small child to eleborate, internally self-consistent worlds created as a hobby or life-long project by adults. Whereas worldbuilding is usually considered a technique to better realisation of setting for a story or group of stories, geofiction can be defined as world creation for its own sake, sometimes but not always to create a story setting, but always for fun. Alternately, geofiction is fiction where the (created) setting is the focus.

A popular example of geofiction is The Lord of the Rings, a book by J. R. R. Tolkien in which he created an entire world (middle-earth) with its own species and races (man, elf, hobbit, etc), imaginary languages and alphabets, all initially for his own amusement.

Micronations are sometimes considered an elaborate form of geofiction.