Sieff is a surname. Notable people with the surname include:
Adam Sieff (born 1954), Communications Director at Dune Music, and a former Sony Music Director of Jazz Annika Sieff (born 2003), Italian ski jumper Israel Sieff, Baron Sieff (1889–1972), British businessman Jeanloup Sieff (1933–2000), fashion photographer Joseph Sieff (1906–1982), businessman and British Zionist Marcus Sieff, Baron Sieff of Brimpton OBE (1913–2001), Jewish British businessman, chairman of Marks & Spencer from 1972 to 1982