Knut Frydenlund (31 March 1927 – 26 February 1987) was a Norwegian diplomat.
His most significant achievement was as Norwegian foreign minister between 1973 and 1981, and again between 1986 and 1987.
Frydenlund was born in Drammen and began his diplomatic career in the 1950s, initially serving at the Norwegian embassy in Bonn, and served in various diplomatic positions during the 1950s and the 1960s.
In 1969 he was elected to parliament as a member of the Norwegian Labour Party, and he became foreign minister in the Labour government in 1973.
While Labour was out of power from 1981 to 1986, he was replaced as foreign minister by Svenn Thorkild Stray, but returned to the office in May 1986.
In February 1987, following his return from a Nordic Council meeting in Helsinki, he collapsed at Oslo's Fornebu Airport due to a cerebral hemorrhage and died soon afterwards at Ullevaal Hospital in Oslo.