"Lady Friend" is a song by the American rock band The Byrds, written by David Crosby and released as a single on July 13, 1967. The single reached number 82 on the Billboard Hot 100 but failed to chart in the United Kingdom. In America and Europe, the B-side of "Lady Friend" was the Chris Hillman song "Old John Robertson", but in the UK, the single's B-side was changed to "Don't Make Waves", a song written by Roger McGuinn and Hillman. The version of "Old John Robertson" found on the B-side of "Lady Friend" is a substantially different mix from the version that would later appear on The Notorious Byrd Brothers album. "Lady Friend" is notable for being the only song penned solely by David Crosby to appear on the A-side of a Byrds' single.

The song was written by Crosby in early 1967 at his home in Beverly Glen in Los Angeles. A demo of the song dating from this period, featuring Crosby accompanying himself on acoustic guitar, was included in the KPFA program The Crosby Connection, during the radio station's February 3, 2001 Grateful Dead marathon. The Byrds' recording of the song has a quick tempo and features chiming guitars, complex vocal harmonies and brass, resulting in the fastest and rockiest single the Byrds had released up to that point. Crosby closely oversaw the protracted recording of the song, much to McGuinn and Hillman's consternation. Tensions in the band increased in the late stages of production when Crosby replaced his bandmates' backing vocals with his own vocal overdubs.

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