Grannis (variation Granniss) is a surname. Notable people with the surname include:
Elizabeth Bartlett Grannis (1840–1926), American editor, publisher and suffragist Kina Grannis (born 1985), American singer-songwriter LeRoy Grannis (1917–2011), American photographer Susanna Grannis (born 1937), American academic Paul Grannis (born 1938), American physicist Pete Grannis (born 1942/1943), American politician Ruth S. Granniss (1872-1954), American librarian