Gamma Hydra IV
Type:	Planet
Location:	Gamma Hydra system Beta Quadrant
Affiliation:	United Federation of Planets

Gamma Hydra IV was the fourth planet in the Gamma Hydra star system.

It once hosted an experimental Federation science colony. Gamma Hydra IV was irradiated by a rogue comet in 2267, killing all six colonists by an unknown radiation type which accelerated the aging of anyone on the surface. The leader of the colony was Robert Johnson, who was married to colonist Elaine Johnson.

The planet was visited for the annual examination of the science expedition by a landing party from the USS Enterprise in 2267, but four colonists were already dead and the Johnson couple dying. Five members of the landing party to Gamma Hydra IV were afflicted by the same radiation; all except one could be healed from the effects. (TOS: "The Deadly Years")