The J'naii were a androgynous humanoid race located on a planet of the same name in the Alpha Quadrant. Most J'naii did not exhibit biological distinctions such as "male," "female," etc. as nearly all other known sentient beings do.
For a time, J'naii society rejected the concept of sexuality completely. The small number of J'naii who appeared to be born into more traditional sexual or anatomical traits were thought to need "therapy" to remove the gender-identification. This was accomplished through the use of psychotectic therapy.
Such a squelching of individuality ran counter to the diverse values of the Federation, a discrepancy that came up when the USS Enterprise-D visited the planet in the 24th century. Commander William Riker began a brief relationship there with Soren, a J'naii who exhibited female physical and psychological traits. The planet's government subsequently used psychotectic treatment to remove "her" remaining thoughts and emotions that were inherently female. (TNG episode: "The Outcast")