Class-M planet with relatively primitive tribal inhabitants. The planet is a rich source of topaline, a rare mineral vital to the life-support systems of many Federation colonies. The U.S.S. Enterprise visited Capella IV in 2267 to secure a mining agreement with the Capellans, but encountered interference from the Klingons.

Capella IV is the home of the Capellan power-cat, a fierce lion-like creature that can discharge 2,000 volts of electricity when touched. The planet is also the source of a beautiful orchidlike flower favored by Dr. Sarah April, one with a lifespan of only a few hours.