|Gamma Hydra IV|
|Location:||Gamma Hydra system|
Gamma Hydra sector
Gamma Hydra IV was an uninhabited M class planet. It was the fourth planet in the Gamma Hydra planetary system. The system was located in the Gamma Hydra sector, which was a region of space in the Alpha Quadrant.
In 2267, Gamma Hydra IV was irradiated by a rogue comet, 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, 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. (The one who could not, Lieutenant Arlene Galway, aged too rapidly and died too soon for the treatment formulated to be used on her.) (TOS: "The Deadly Years")