John Fremont Melby (July 1, 1913 – December 18, 1992) was a United States diplomat, who served in Soviet Russia from 1943 to 1945 and in China from 1945 to 1948. He held other positions with the Department of State until 1953, when he was dismissed as a security risk because of his long and intimate association with the playwright Lillian Hellman, who was accused of communist ties. He later became an academic specializing in Far Eastern affairs.