Bob Dylan started his career in folk music.
Dylan moved to New York City in January 1961 and immersed himself in the Greenwich Village folk scene. He performed in clubs, learned songs from established folk musicians, and drew major inspiration from Woody Guthrie, whose socially conscious songwriting strongly shaped Dylan's early style. His first public reputation was as a folk singer and songwriter rather than as a rock performer.
Dylan's self-titled debut album, released in 1962, included traditional folk, blues, and gospel material alongside two original songs. His breakthrough followed with The Freewheelin' Bob Dylan in 1963, which established him as a major singer-songwriter through songs such as “Blowin' in the Wind” and “A Hard Rain's a-Gonna Fall.”
The common mix-up comes from Dylan's later transformation. In 1965, he used electric instruments at the Newport Folk Festival and released increasingly rock-oriented albums including Bringing It All Back Home and Highway 61 Revisited. That shift made him central to rock history, but it came after his career had begun in the folk tradition. Folk is therefore the single canonical answer.