(covers information from several alternate timelines)
Designated as a "pleasure planet", Risa was an inhabited Federation planet located in a binary system, in orbit of the star Epsilon Ceti B, and was about ninety light years from the Sol system. The planet was orbited by at least two moons.
This planet was the homeworld of the humanoid Risians and its planetary government was called the Risa Hedony. (TNG: "Captain's Holiday"; ENT: "Two Days and Two Nights"; Star Trek Into Darkness; PIC: "Maps and Legends")
Culture and climate
Risa was originally a dismal, rain-soaked, and geologically unstable planet covered with vast jungles and plagued by violent earthquakes. However, the planet was transformed by the native Risians with a technologically sophisticated weather control system that provided almost-constantly desirable weather, industrial replicators, and seismic regulators to eliminate the geological instability for optimum tourist comfort. By at least the mid-22nd century, Risa became known for its beautiful tropical resorts and an abundance of pristine beaches, making it a popular tourist destination. (ENT: "Two Days and Two Nights"; TNG: "The Mind's Eye"; DS9: "Let He Who Is Without Sin...")
Risa was most noted for its native population having a frank and open attitude to sexuality. By the mid-24th century, Risa had developed a reputation as being a most peaceful planet, where weapons weren't allowed. (TNG: "Captain's Holiday"; DS9: "Let He Who Is Without Sin...")
In 2371, after surviving an attack by the Vidiians, Kathryn Janeway and Chakotay remembered a "cautionary tale" told to Starfleet Academy cadets before their first shore leave on the planet. In the tale, a man goes to Risa, meets an alluring woman who seduces him into what he thinks will be an evening of passion. Upon awakening in the morning, he feels awesome but discovers that he's missing a kidney. (VOY: "Fury")
- Suraya Bay, where the Lohlunat, the Festival of the Moon, was held. One recommended restaurant was a little boat that sailed into the bay every evening, just after sunset. Patrons waded out to it, and they were served seafood right off the deck. (ENT: "Two Days and Two Nights")
- Galartha, a cliff face that changed pitch while a person climbed it. (ENT: "Two Days and Two Nights")
- Temtibi Lagoon, where it never rained, the water was warm and the wind smelled sweet. (DS9: "Let He Who Is Without Sin...")
- Subterranean gardens with luminescent plants. (ENT: "Two Days and Two Nights")
- Risan steam pools, which were said to be very relaxing. (ENT: "Two Days and Two Nights")
- The Risa water recreation park. (VOY: "Riddles")
There were many nightclubs on Risa, but the Vulcan database advised visitors to be wary of occasional crimes. Commander Tucker and Lieutenant Reed, for example, were left tied up in their underwear by two alien thieves who had been disguised as two "gorgeous" Risian females. (ENT: "Two Days and Two Nights")
In 2152, Enterprise NX-01 visited Risa for two days for some shore leave. This stopover marked the first official visit of an Earth starship to Risa and also the farthest any Human had officially traveled from the Sol system up until then. (ENT: "Two Days and Two Nights")
Also during the 22nd century, a time-traveling scientist from the 27th century named Kal Dano came to Risa. There he hid an invention of his called the Tox Uthat – a device capable of halting all nuclear fusion within a star – from Vorgon criminals who considered it to be a formidable weapon.
Risa was a common travel destination during the mid-23rd century. During the Federation-Klingon War of 2256, two crewmen aboard the USS Discovery laughed about someone who had never been to Risa. (DIS: "Context Is for Kings")
In 2366, Vash, a Human archaeologist who was concluding years of search by Professor Samuel Estragon, found the Tox Uthat buried in a cave. She wanted to conceal her discovery from other interested factions, such as vacationer Jean-Luc Picard, but as Picard discovered her deception and the Vorgon's longing for the dangerous device, he destroyed it. (TNG: "Captain's Holiday"; DS9: "Q-Less")
According to Starfleet Security, it was believed that Federation Ambassador Krajensky was kidnapped by the Dominion while visiting Risa in 2371 so that he could be replaced by a Changeling impersonator. (DS9: "The Adversary")
In 2373, the New Essentialists Movement, who led a campaign to turn the Federation away from its perceived decadence, successfully sabotaged Risa's weather control system. They attempted to do the same to the planet's vital seismic regulators, but were stopped when Lieutenant Commander Worf became disillusioned with them and refused to continue the demonstration. (DS9: "Let He Who Is Without Sin...")
In 2135, while working for the Vulcan Ministry of Security, T'Pol tracked down the fugitive Vulcan operatives Menos and Jossen to Risa and pursued them into the planet's Tropical Zone jungles. She killed Jossen, but Menos escaped. She was later dismissive of her activities there upon Enterprise's 2152 visit, saying merely, "I've visited Risa before. It seemed appropriate to give someone else a chance." (ENT: "The Seventh")
During Enterprise's two days and two nights on Risa, crewmembers enjoyed various locations, such as Suraya Bay and the Galartha cliffs. While visiting there, Captain Jonathan Archer met a couple who were also visiting the planet, where they were celebrating their three hundredth wedding anniversary. (ENT: "Two Days and Two Nights")
Geordi La Forge was scheduled to attend an artificial intelligence seminar on Risa in late 2367. He was ordered by Captain Picard to arrive a few days early to have some fun and relax. However, several hours before his arrival, he was kidnapped by Romulans and replaced by a double who attended the seminar in his place. (TNG: "The Mind's Eye")
Hoping to stop her from further helping the Maquis, Benjamin Sisko told Kasidy Yates they should visit Risa. Yates turned him down, but told him she would meet him there if he wanted to travel there alone in a runabout. (DS9: "For the Cause")
At some point in 2373, Raimus was on Risa and talked a Starfleet officer who was in command of the weather control system there into becoming an informant for the Orion Syndicate. (DS9: "Honor Among Thieves")
When Grand Nagus Zek disappeared in mid-2375, Quark believed he was probably on Risa. In fact, he had traveled to the mirror universe. Zek himself knew that Quark would say he was on Risa. (DS9: "The Emperor's New Cloak")
Following the Battle of Cardassia and the prospect of a larger battle with the Dominion, Ezri Dax told Captain Sisko, "All things considered, I'd rather be on Risa." Sisko noted, "That makes two of us." (DS9: "What You Leave Behind")
Points of interest
There are two pronunciations for Risa. In the script for "The Mind's Eye", the pronunciation was "RYE-sa".  In the script for "Q-Less"", the pronunciation was "RYE-suh".  The latter pronunciation was used in the script for "Fallen Hero".
The concept of Risa was invented by Ira Steven Behr, who based the script for the episode "Captain's Holiday" on it. Gene Roddenberry approved of the idea of the "pleasure planet" but wanted to radically change Risa's culture to incorporate extremely graphic depictions of homosexual behavior, which Rick Berman advised Behr to ignore. (William Shatner Presents: Chaos on the Bridge)
Years after working on Star Trek: The Next Generation, Patrick Stewart once claimed that Risa was the only planet from TNG that he could remember the name of. (William Shatner Presents: Chaos on the Bridge)
For DS9: "Let He Who Is Without Sin...", sets representing guest chambers on Risa (such as Pascal Fullerton's, as well as one used by Worf and Jadzia Dax) were built on Paramount Stage 17. (citation needed • edit)
In ultimately omitted dialogue from the final draft script of ENT: "Desert Crossing", Jonathan Archer and Charles Tucker III agreed that, when they arrived on Risa, the first thing they would do would be to "jump into the nearest swimming pool" they could find. In the same script, Risa was depicted as appearing in the episode's final shot, referred to in a scene description as "a beautiful, blue-green planet," despite the fact Risa does not appear in that episode's final version. Nonetheless, Risa was also referred to as a "blue-green planet" in the final draft script of ENT: "Two Days and Two Nights" and in incomplete visual effects footage from a deleted scene excluded from that episode (the latter of which can be seen in the special features of the ENT Season 1 DVD and Blu-ray).
In the version of the ultimately deleted scene from the final draft script of "Two Days and Two Nights", a scene description stated, "Risa hangs enticingly outside the windows," and another scene description mentioned "the promise of Risa shining through the windows." The filmed version of the scene demonstrates that, if the scene had been completed, the planet would have been inserted into the footage with replacement of green screen.
In another scene description from the final draft script of "Two Days and Two Nights", Risa was referred to as a "spectacular planet." The surface of the planet was also scripted to be extremely serene.
In a scene that was scripted for the end of ENT: "Home" (and included in the ENT Season 4 Blu-ray) but never filmed, Risa was briefly mentioned, as one of several small rocks which Archer left at his father's grave had been taken, by the captain, from Risa. In the same scene, Archer commented, as if to his deceased father, "That's a place I wish you could've seen."
A reference to Risa was included in the first draft script of the aborted film Star Trek: The Beginning, set in 2159. Risa was noted to be the location where Archer and Enterprise were during a series of Romulan attacks in the Sol system, which took place on 13 August 2159 and initiated the Earth-Romulan War.
At the conclusion of DIS Season 1, After Trek host Matt Mira commented to Sonequa Martin-Green and Anthony Rapp that he thought the USS Discovery's crew should set a course for Risa. Martin-Green agreed with this, since the Federation-Klingon War depicted in the series was now over, but Mira had to explain to her what Risa was before she understood. (AT: "Will You Take My Hand?")
A logo for Risa, depicting a sunset over an ocean, was created and shown in VOY: "Inside Man", on Deanna Troi's beach towel. A more colorful version was used in the reference book Star Trek: Star Charts (p. 53).
According to Star Trek: Star Charts (pp. 53, 56), the planet Risa (Epsilon Ceti B II) was class M and its government was the Risan Hedony. This planet was admitted into the United Federation of Planets in 2249. The Risan capital was Nuvia. The population of Risa, which included Risans and individuals from many other species, in 2378, was 2.81 billion, and, in an average year, up to 1.3 billion tourists visited the world. Points of interest included Temtibi Lagoon, Suraya Bay, and the Eluvian Mud Baths. The tropical climate was controlled by a weather control system. In the 24th century, Risa was a popular destination on the major space lanes.
The Star Trek Encyclopedia (4th ed., vol. 2, p. 225) described Risa as a tropical class M planet.
According to the RPG sourcebook Planets of the UFP, Risa was the third planet in the Tau Regulon system.
According to the RPG sourcebook Worlds, Risa was the third planet in the Granicus system.
Before ENT: "Rajiin" established Nuvians to be a separate species, the reference to Nuvian masseuses on Risa in ENT: "Fallen Hero" was misinterpreted by the non-canon Star Trek: Star Charts, which lists the city of "Nuvia" as the capital of Risa.