The St. John's College Choir (or Choir of St. John's College), Cambridge, is one of Britain's most renowned, and venerable collegiate choirs in the cathedral tradition, consisting of adult males (in this case undergraduate students) and boys. The group is especially notable for the wide range of its repertory, represented on dozens of recordings.

Music has been sung at St. John's since the college was established in 1511, and the formation of a distinct Choir of St. John's College dates to the 1660s and 1670s; George Loosemore, an organist, was listed in payroll records as a teacher of the choristers from 1661. In the 19th and 20th centuries, the choir's music directors sometimes remained in their posts for decades: George Garrett, the composer of the Anglican chant melody for Psalm 126, held the position from 1857 to 1897, and George Guest was music director from 1951 to 1991. The choir has always sung for daily Church of England services at the St. John's College Chapel, but it was Guest who built its busy schedule of broadcasts on BBC radio, and later television, leading the choir to what has become an extensive catalog of recordings. A George Guest medal is now awarded each year to an outstanding boy chorister. Since Guest, the choir's music directors have been Christopher Robinison (1991-2003), David Hill (2003-2007), and since 2007, Andrew Nethsingha. The music director is assisted by one or more organ scholars.

The choir is fairly large by modern-day standards, including 20 boy sopranos; within their ranks are 16 choristers and four probationers, selected from among seven- and eight-year-old applicants who pass a set of voice trials. The alto, tenor, and bass parts are sung by a group of 15 choral scholars, referred to as lay clerks. Lay clerks are either undergraduates at St. John's College, or in a few cases, recent graduates. These members are not necessarily music students at St. John's College. These groups have spawned individuals who have gone on to impressive musical careers; these include countertenor Iestyn Davies, choral conductor Stephen Cleobury, and early music performer and conductor Andrew Carwood.

The choir renews various traditions, including the Ascension Day Carol, where they sing from the chapel's tower roof (163 feet high). This tradition began in 1902 when the choir's director, Cyril Rootham, agreed to a bet with Sir Joseph Larmor; Larmor believed the choir could not be heard from that height, but the choir demonstrated Rootham to be the winner of the bet.

The choir has commissioned numerous works from contemporary composers dating back to Herbert Howells, who served as a temporary organist during World War II. They perform and record music from the European continent to a greater degree than most other English collegiate or cathedral choirs. The St. John's College Choir has recorded for major labels including Chandos, Hyperion, Naxos, and Signum Classics. In 2019, the group released Locus iste, a collection of 20th century choral music on Signum Classics. ~ James Manheim, Rovi