The Ligonians were the humanoid inhabitants of the planet Ligon II. Although they possessed transporter technology, they were extremely antiquated in other ways and were not as technologically advanced as the Federation. (TNG: "Code of Honor") Their contact with the Federation dated back to at least the 2320s. (TNG: "The First Duty")
In 2364, Captain Jean-Luc Picard of the USS Enterprise-D stated "we are aware of many of [...] the achievements [of Ligon II], and its unique similarity to an ancient Earth culture we all admire.", thus implying social parallels between the Ligonians and (a) historical Earth culture(s).
Ligonians had a highly structured society and were an extremely proud species. They valued their honor above all else, and as such lived by strict codes of honor. They also valued patience highly and were always apprehensive about strangers. Ligonians generally resembled Humans of Sub-Saharan African descent physically.
In Ligonian society, the females owned all the property and land. When a man married a woman, he gained control of her wealth, and it passed to him when she died. A man could take a number of wives, and similarly a woman could have a number of husbands. The favored spouse was referred to as the "First One". If a man wished to take a new First One, the current First One had the right to challenge the newcomer in a fight to the death, although this was rare.
Many Ligonian males wore necklaces consisting of a golden strap and a red jewel. Lutan's necklace contained a hidden transporter device. When he pressed the red jewel, he would be beamed away by a Ligonian transporter beam. He used the device to escape from the Enterprise-D with security chief Natasha Yar as his hostage, exercising a form of counting coup. The necklace also had a ceremonial meaning. When Yareena, Lutan's First One, was killed (and later revived) in the fight between her and Tasha Yar, her mating agreement with Lutan had dissolved. She chose Hagon as her new mate instead and gave him the necklace, thereby stripping Lutan of all his powers and making Hagon the new ruler of Ligon II.
Ligonians tapped together two carved ivory-like sticks to signal applause or approval.
While Jean-Luc Picard was a cadet at Starfleet Academy, he once wrestled a Ligonian and caught him "with a reverse body lift and pinned him down in the first fourteen seconds of the match," according to Academy groundskeeper Boothby, who was very much surprised by the feat at that time. Picard stated that the win "was all in the legs." (TNG: "The First Duty")
The Ligonian guards used long spears while guarding people or objects. As seen on the centerplace of Lutan on Ligon II they also used bladed weapons including axes and knives and other hand-held weapons such as a crossbow. (TNG: "Code of Honor")
An original story concept by the episode writers Kathryn Powers and Michael Baron named the Ligonians Tellisians, a reptilian species with a culture similar to the Japanese samurai. (Creating the Next Generation, p.39)
Many members of the production staff, including Tracy Tormé and Jonathan Frakes, objected to the casting of all the Ligonians seen in "Code of Honor" as racist, especially as they were portrayed in stereotypically "tribal" roles. (Star Trek: The Next Generation Companion 2nd ed., p. 34; )
The FASA RPG Star Trek: The Next Generation First Year Sourcebook established that the Ligonians have a life span of 94 years.
In the Star Trek: Starfleet Corps of Engineers eBook Turn the Page, the USS da Vinci was assigned to repair a Ligonian orbital control station. The encounter with the Ligonians was Carol Abramowitz's first away mission.