Keith Reid (born Keith Stuart Brian Reid, 19 October 1946, Welwyn Garden City, Hertfordshire, England) is a songwriter who wrote the lyrics of every Procol Harum song that is not a cover. For many years he resided in the United States.

Although he did not sing or play an instrument, lyricist Reid was a pivotal element to the long-term success of Procol Harum, teaming with vocalist/composer Gary Brooker to write most of the group's material. (Some music was written by organist Matthew Fisher and by guitarist Robin Trower.) Reid left school at the age of 15 and soon began writing lyrics, inspired primarily by Bob Dylan. Through Island Records chief Chris Blackwell, Reid was introduced to R&B impresario Guy Stevens, who in turn introduced him to fledgling composer Brooker in 1966. The two began collaborating, and upon compiling a number of songs set about assembling a band to record their material; with the Procol Harum line-up in place, they first recorded "A Whiter Shade of Pale", which set Reid's surreal lyrics to a Brooker melody inspired by Johann Sebastian Bach. The single topped the UK Singles Chart for six weeks in mid 1967, going on to sell over six million copies worldwide. For his efforts, Reid was credited as an official member of the group, and he wrote all of Procol Harum's lyrics through to the band's 1977 demise.
Reid then set up his own management firm, Full House, working on a play and relocating to Manhattan in 1986; three years later, Brooker contacted him to discuss reuniting Procol Harum and the group's comeback album, The Prodigal Stranger, was issued in 1991.

In August 2008 a new album, The Common Thread, was issued under The Keith Reid Project banner. Reid wrote the lyrics for the songs, which were performed by a variety of musicians, including Southside Johnny, Chris Thompson, John Waite and Michael Saxell.