Fredrik Stang Heffermehl (born 11 November 1938) is a Norwegian jurist, writer and peace activist.
He formerly worked as a lawyer and civil servant from 1965 to 1982 and was the first secretary-general of the Norwegian Humanist Association from 1980 to 1982.
He later made his mark as a writer and activist for peace and against nuclear arms.
He is the honorary president, and former president, of the Norwegian Peace Council, a former vice president of the International Peace Bureau, which received the 1910 Nobel Peace Prize, and a former vice president of the International Association of Lawyers against Nuclear Arms.