Manley Augustus Buchanan (born 19 April 1949, Trenchtown, Kingston, Jamaica), better known as Big Youth (sometimes called Jah Youth), is a Jamaican deejay, mostly known for his work during the 1970s.

He commented, "Deejays were closest to the people because there wasn't any kind of establishment control on the sound systems".

Before beginning his musical career, Buchanan worked as a diesel mechanic at Kingston's Sheraton Hotel, where he would develop his toasting skills while he worked, and was nicknamed "Big Youth" by his co-workers. He started to perform at dances, initially influenced by U-Roy, and became a regular with Lord Tippertone's sound system by 1970, becoming the resident deejay, and attracting the attention of Kingston's record producers. His early singles for producers such as Jimmy Radway ("The Best Big Youth"), Lee Perry ("Moving Version") and Phil Pratt ("Tell It Black") were artistically and commercially unsuccessful.

By 1972 he had begun working with Augustus "Gussie" Clarke, a teenage producer whose rhythms and singers were more in tune with the vibes on the streets of Kingston, and "The Killer" (on a version of Horace Andy's "Skylarking" rhythm) became his first major Jamaican hit, soon followed by "Tippertone Rocking". Following this, he released the hugely successful "S-90 Skank", featuring a motorbike being revved in the studio, for Keith Hudson's Imbidmts label, versioning the producer's own "We Will Work It Out". This became his first Jamaican number one hit, and also featured in a television advert for the Honda motorcycle that inspired it. The first album to feature his vocals, Chi Chi Run was produced by Prince Buster in 1972. Distinctive musically, his half-sung style contrasting with his contemporaries, he was also visually distinctive, with his teeth inlaid with red, gold, and green jewels.

In 1973 he released his first album entitled Screaming Target, produced by Gussie Clarke. The album is still considered as a classic of its genre, featuring rhythms from well-known hits by Gregory Isaacs, Leroy Smart, and Lloyd Parks, among others. Around this time, he also notched up some achievements in the singles chart, having seven singles in the chart at one time, and having four singles remain in the top 20 for an entire year. Throughout 1974 and 1975 he continued to record for other producers, including Glen Brown ("Dubble Attack"), The Abyssinians ("I Pray Thee"/"Dreader than Dread"), Yabby You ("Yabby Youth" - later known as "Lightning Flash (Weak Heart Drop)"), Bunny Wailer ("Bide"/"Black on Black") and Joe Gibbs ("Medecine Doctor").

His next LP, Dread Locks Dread, was released on Klik Records in 1975. Although ostensibly a Big Youth LP produced by "Prince" Tony Robinson, it in fact only featured six vocal tracks, two of which - "Marcus Garvey Dread" (originally "Mosia Garvey" on Jack Ruby's Fox label) and "Lightning Flash" had been released as singles for other producers.

By this time he had begun releasing his own self-produced recordings on the Negusa Nagast and Augustus Buchanan labels in Jamaica, sometimes buying rhythms from producers for whom he had worked, but latterly using his own musicians, usually the Soul Syndicate band. Many of his singles, such as "Hot Stock", and "Battle of the Giants" (with U-Roy) were released on this imprint. His first self-produced LP was Reggae Phenomemnon in 1974. His self-productions continued with Natty Cultural Dread in 1976, followed later that year by Hit the Road Jack. Having recorded only deejaying records initially, by now Big Youth was developing more confidence as a singer; while his vocal range was never the greatest, his singing sides continued to improve in musical quality, and began to become as common as his DJ tunes. This was helpful, as new young DJs such as Trinity and Clint Eastwood were appearing on the scene, and Big Youth's chanting style was becoming less fashionable.

He signed to Virgin Records' Frontline label in 1977, his first release on the label being the Isaiah First Prophet of Old album, and he also appeared in the film Rockers. Virgin declined the chance to release his next three albums, however, and as the 1970s came to a close, Big Youth's popularity took a dip. By the early 1980s, events had combined to make reggae much less successful than it had been five years earlier. The rising tide of violence had driven many musicians and producers to leave Jamaica for the UK and U.S., reggae had not broken through to widespread commercial success, and, in the wake of Bob Marley's death a lot of major labels either dropped their Jamaican artists or spent little on promoting them, and the music returned to its insular roots. "Slackness" (sexually explicit lyrics) became far more fashionable than cultural Rastafari movement, and teenagers looked more towards the United States for their heroes. While his records continued to find a market, tunes like "Jah Jah Golden Jubilee", "A Luta Continua" and "Chanting" failed to capture the public imagination.

The modern digital rhythms were far from suited to Big Youth's style, and his forays into the studio became less frequent. His appearance at Reggae Sunsplash in 1982 (he would appear another four times between 1983 and 1996) was well received, but his success during the 1980s was limited. His career revived in 1990, with the "Chanting" single, produced by Winston "Niney" Holness, and "Free South Africa" on the protest album One Man One Vote.

"Yes, me come inna de music as Rasta, me a de original rastaman who enter it." –Big Youth, Italy, 2001