Talin VIII was a gas giant planet in the Talin system, in or near Federation space.
In 2269, following the disaster at Talin IV, it was discovered that events there had been manipulated by an ancient, primitive lifeform dubbed "the Many". By triggering the mass release of nuclear radiation, the planet's biosphere was altered to promote the growth of a certain strain of purple waterborne algae, intended for consumption by a symbiotic lifeform, called "the One". To preserve this world and its native race, the Starfleet Corps of Engineers launched a sixty-year project to convert Talin VIII into the food source for the One instead. (TOS novel: Prime Directive)