The Nation of Celestial Space (also known as Celestia) is a micronation created by James Thomas Mangan.

Celestia comprised the entirety of "outer space", which Mangan laid claim to on behalf of humanity to ensure that no one country might establish a political hegemony there.

As "Founder and First Representative", he registered this acquisition with the Recorder of Deeds and Titles of Cook County on January 1, 1949.

Later, as the space race got underway in earnest he sent angry letters of protest to the leaders of the Soviet Union and United States on the occasions that their early space flights encroached upon his claimed territory - although he later waived these proscriptions to allow for satellite launches by the latter.

Its only surviving legacy is the series of stamps and silver and gold coins and passports issued in its name by Mangan from the late 1950s through to the mid-1960s.