John Frith may refer to:

• John Frith (assailant) (fl. 1760–1791), English petitioner and asylum inmate
• John Frith (cartoonist) (c. 1908–2000), Australian cartoonist, at The Herald in Melbourne in the 1950s and 1960s
• John Frith (martyr) (1503–1533), English Protestant martyr
• John Frith (rugby league) (born 1985), Australian rugby league player
• John Frith (trade unionist) (1837–1904), British trade union leader