DNA confirmed people with O surname
- Florence O'Brien ( - 1967)
- Jay Geddes Odell (1911 - 2000)
- Jonas Bertilsson Ofwerman (1706 - 1772)
- Anna Olfert (ABT 1872 - ABT 1935)
- Isaak Olfert (ABT 1845 - ABT 1890)
- Elizabeth Oliphant (1785 - 1854)
- Obadiah Oliphant (ABT 1741 - 1833)
- Margaret Frances Olives (28 Feb 1925 - 31 Jan 1988)
- Lila Juanita Olives (ABT 1922 - ABT 1992)
- Robert Lee Olives (10 Aug 1927 - 14 Mar 2017)
- Charles Milo Olives (16 Jun 1908 - 1966)
- Melba Myrtle Olives (28 Aug 1918 - 31 Dec 1978)
- Rid Thomas Olives (25 Sep 1884 - 26 Jan 1952)
- Barbara Sally Ollis ( - 1915)
- Brita Olofsdotter (1703 - 1776)
- M Oosterink (1932 - 2015)
- Anton Oquist (1840 - )
- Harry Anton Oquist (1888 - 1942)
- Ellen Harriet Oquist (1914 - 2011)
- Amie Overby (1812 - ABT 1867)
- Archibald Overby (1796 - ABT 1878)
- Mary Elizabeth Overby (ABT 1830 - 13 Mar 1898)
- Nicholas Overby (ABT 1776 - ABT 1857)
- Caroline Priscilla Overby (ABT 1840 - 10 Mar 1907)