Tønseth is a surname. Notable people with the surname include:
Didrik Tønseth (diplomat) (born 1944), Norwegian diplomat and lawyer Didrik Tønseth (skier) (born 1991), Norwegian cross-country skier Erik Tønseth (born 1946), Norwegian jurist and industrialist Jan Jakob Tønseth (1947–2018), Norwegian author, poet and translator Per Tønseth (1914–1993), Norwegian judge