Johanna Martzy (26 October 1924 – 13 August 1979) was a Hungarian violinist.
She was born in Timișoara, Romania in 1924 and debuted at 13. She toured in the 1940s and 1950s. After that decade her renown in North America, at least, declined and her death from cancer, in Glarus in 1979, was not well noted.
She was referred to by Glenn Gould in his essay "We who are about to be disqualified salute you," as "an artist who has always seemed to me to be, at least in North America, the most underrated of the great violinists of our age."
She won 1st prize at Geneva competition in 1947.