János Kajdi (30 December 1939 – 10 April 1992) was a boxer from Hungary.
He competed at the 1964, 1968 and 1972 Olympics in the lightweight, light-welterweight and welterweight (– 67 kg) division, respectively, and won a silver medal in 1972.
In the final he was defeated by Cuba's Emilio Correa on points (5:0).