Newth is a surname. Notable people with the surname include:
Brian Newth (born 1947), New Zealand modern pentathlete David Newth (1921-1988), British zoologist Eirik Newth (born 1964), Norwegian astrophysicist George Samuel Newth (1851–1936), English chemist Jonathan Newth (born 1939), British actor Mette Newth (born 1942), Norwegian illustrator and author of children's literature Philip Newth (born 1939), Anglo-Norwegian author of children's literature