"Triad" is a song written by David Crosby in 1967 about a ménage à trois, a subject perfectly in keeping with the "free love" hippie philosophies of the day. The song was written while Crosby was a member of the rock band The Byrds, who were at that time recording their fifth studio album, The Notorious Byrd Brothers. Although the band did record "Triad" and perform it live during a September 1967 engagement at the Whisky a Go Go, it was not included on The Notorious Byrd Brothers album. According to Crosby, Roger McGuinn and Chris Hillman felt that its subject-matter was too controversial, McGuinn allegedly deriding the song as a "freak-out orgy tune." However, this has since been denied by Hillman who has stated "I don't think it was a moral decision. The song just didn't work that well. David was drifting and bored and wanted to do something else, and that song just added fuel to the fire."
There had been growing animosity between Crosby and the rest of the band throughout 1967. Tensions had arisen from several factors, including Crosby's displeasure over the band's wish to record the Goffin–King composition "Goin' Back", his fraternization with fellow L.A. musicians, and his controversial remarks to the audience during The Byrds' performance at the Monterey Pop Festival. These factors, along with the discord over "Triad", contributed to McGuinn and Hillman's decision to fire Crosby in October 1967. Crosby gave the song to Jefferson Airplane, who recorded it on their 1968 album, Crown of Creation. A live recording of "Triad" was later included on Crosby, Stills, Nash & Young's 1971 album, 4 Way Street.
The song's lyrics were largely inspired by the sexual freedom that Crosby enjoyed at his home in Beverly Glen in Los Angeles. However, the song also features allusions to author Robert A. Heinlein's science fiction novel Stranger in a Strange Land, with references to "sister lovers" and "water brothers". "Triad", as recorded by The Byrds, remained unreleased for twenty years until the 1987 archival album, Never Before. It also appears on the The Byrds box set from 1990, as a bonus track on the 1997 Columbia/Legacy reissue of The Notorious Byrd Brothers, and on the 2006 There Is a Season box set.
The Icicle Works recorded "Triad" as a medley with another Byrds' song, "Chestnut Mare", on the 1989 Byrds' tribute album Time Between – A Tribute to The Byrds. The song was also covered by Danish singer-songwriter Tina Dico in 2008.