The L-5 Colonies were a series of six asteroids in Earth orbit which were hollowed and colonized prior to World War III. In 2031, in one of the last major acts of international cooperation before World War III, asteroid fragments were diverted. These were refered to as O'Neil-style space habitats: Vanguard colony, Colony Roykirk, the Moss-Offenhouse colony, the NicholCorp facility, the Brynner Asteroid, and the Starling Habitat.

By 2053, all six colonies were sufficiently self-sustaining that they all survived the nuclear exchanges and subsequent chaos. In 2058, in cooperation with Zefram Cochrane at "Earth Station Bozeman", the colonies participated in a test to generate a stable subspace field. However, due to an unknown error during the test, all six colonies vanished and were presumed destroyed.

In fact, Vanguard colony was not destroyed but flung some 200,000 light years from Earth. The survivors became known as the Neyel. Vanguard colony was later saved from destruction, and returned to local space by the USS Titan and a Romulan fleet. (TLE novel: The Sundered, TTN novel: The Red King)

Terise Haleakala-LoBrutto later compared the early Vulcan/Romulan generation ships to the L-5 Colonies. (TOS novel: The Romulan Way)