|Location:||Denobula Triaxa system|
Denobula was heavily populated, with approximately twelve billion inhabitants as of 2152, 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"
Shortly before Star Trek: Enterprise was cancelled at the end of its fourth season, Phlox actor 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.