|Location:||Denobula Triaxa system|
|Affiliation:||Coalition of Planets|
As of 2152, Denobula was heavily populated, with approximately twelve billion inhabitants, all living on the planet's only continent. The cities were quite crowded, though Phlox noted that the atmosphere was "vibrant, communal". The riverside nightclubs of the Kaybin District were known as meeting places to find intimate partners during the Denobulan mating season. (ENT: "Dear Doctor", "Doctor's Orders", "The Catwalk")
- "Fight or Flight" (referred to as homeworld)
- "Breaking the Ice" (first mention of Denobula)
- "Dear Doctor"
- "Vanishing Point"
- "The Catwalk"
- "The Crossing"
- "The Breach"
- "Doctor's Orders"
- "Cold Station 12"
- "Terra Prime"
Background information Edit
Denobula was mentioned in voiceover dialogue that was scripted for ENT: "Dear Doctor" but not included in the final version of that episode; at one point, Phlox said that miners who had been assigned, along with him, to a Denobulan mining facility on Pree'nos had tried to make their compound as much like Denobula as they could (such as with "entertainment from home"), though that hadn't seemed right to him. The planet was likewise referred to once in the final draft script of ENT: "Detained" but not in the final edit of that installment.
Phlox actor John Billingsley imagined the Denobulan homeworld as a utopia, to the point of causing the Denobulans to become insular. "I mean, maybe it's so Eden-like [on Denobula]," he reckoned, "that it's like, 'Oh, what do I want to go out there for? I've got everything that I want right here.'" (Star Trek Monthly issue 95, p. 43)
Shortly before Star Trek: Enterprise was cancelled at the end of its fourth season, John Billingsley expressed an interest in viewing Denobula on the series, saying, "I would love to see a visit to Denobula."  In fact, Manny Coto once stated that, if the series had gone into a fifth season, Enterprise would indeed have visited the planet. 
According to the Star Trek: Star Charts (pp. 36, 44, "United Federation of Planets"), the Denobula Triaxa system, also known by its Bayer designation as Iota Boötis, was located in or near Federation space, in the Alpha Quadrant. Denobula Triaxa A was a G class star with a magnitude of +7, which was 1/10 the brightness of Sol. Denobula Triaxa B and C were G class stars. In the mid-22nd century, Denobula was a destination on the Earth-Denobula, Fellebia-Denobula, Neethia-Denobula, Pyrithia-Denobula, Pree'-Denobula, and Vulcan-Denobula runs. In 2378, Denobula was a Federation member.
According to the reference book Star Trek: Federation - The First 150 Years, a Romulan force attacked Denobula and its orbiting spaceport in 2158. The ambush resulted in over three million casualties and intimidated Denobula, causing it to refrain from supporting the Coalition of Planets during the Earth-Romulan War.