(covers information from several alternate timelines)
Deneva, also known as Deneva Prime, was a Human-inhabited planet orbiting the Alpha Quadrant star Deneva. Hosting the Deneva colony and Deneva Station, the planet was considered one of the most beautiful worlds in the galaxy.
The Deneva colony was established on this planet in the mid-22nd century, originally as a freighting-line base in the area. Supplies would be sent to the miners in the system's asteroid belt and what was mined in the asteroids would be sent back to Deneva for transfer to other Earth, and later Federation, worlds and colonies. In 2267, there were over a million inhabitants on this world, with more than a hundred thousand living in the capital city alone. The nearest starbase was Starbase 10. (TOS: "Operation -- Annihilate!", ENT: "Horizon", "Rogue Planet")
In late 2266 – eight months before the visit of the USS Enterprise – space vessels from Ingraham B brought an infestation of flying parasites. These parasites would have wiped out the colony, as they had Ingraham B and at least three other civilized worlds, had not Captain Kirk and his crew destroyed them. Many people died from the infestation, including Kirk's brother Sam, just before the arrival of the Enterprise, and his wife Aurelan, soon after. The couple had moved to the planet with their son Peter not long before the infestation. (TOS: "Operation -- Annihilate!")
Dr. Gabrielle Burnham's mission logs from a future timeline, viewed by Michael Burnham in 2257, listed Deneva among the devastated worlds where Control had wiped out all life by the 33rd century. (DIS: "Perpetual Infinity")
The city exteriors for Deneva were shot on location at the TRW Space and Defense Park in Redondo Beach, near Los Angeles. Filming took place on Wednesday 15 February 1967. The establishing shot of Kirk's brother's lab was a building on the campus of UCLA, and the entrance to the building was the cafeteria at TRW. (Star Trek Encyclopedia (4th ed., vol. 1, p. 202)) (These Are the Voyages: TOS Season One)
According to Star Trek: Star Charts (pp. 36, 45, "United Federation of Planets I") and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), in 2120, Zefram Cochrane visited this planet on his final voyage. In the mid-22nd century, Deneva was a destination on a Vulcan trade route. In 2378, Deneva was a Federation member.
According to Star Trek Maps, Deneva was the third planet in its system.
According to the RPG sourcebook The Federation, Deneva was the fourth planet in the Beta Darius system.