*[[o:l_oatley|Lottie Oatley (1876 - 1961)]]
  *[[o:a_obrien|Anna Josephine O'Brien, nee Brazil (d. 1924)]]
  *[[o:c_obrien|Charles Thomas O’Brien (1896 – 1918)]]
  *[[o:co_obrien|Colon Henry O’Brien (1894 - 1917)]]
  *[[o:g_obrien|George Andrew Martin Lane O'Brien (1864 - 1901)]]
  *[[o:j_obrien|James Jonathon O’Brien (b. 1894)]]
  *[[o:jo_obrien|John O'Brien]]
  *[[o:r_obrien|Rick O'Brien]]
  *[[o:t_obrien|Thomas William O'Brien (1862 - 1916)]]
  *[[o:w_obrien|William John “Bill” O’Brien (1878 – 1918)]]
  *[[o:d_oconnor|Dennis “Dinny” O’Connor (d. ~1939)]]
  *[[o:h_oconner|Hubert O'Connor OMI]]
  *[[o:p_odonoghue|Padraig “Paud” O’Donoghue (1922 – 2009)]]
  *[[o:d_odonovan|Declan O’Donovan (b. 1985)]]
  *[[o:di_odonovan|Diarmuid O’Donovan (1946 – 2023)]]
  *[[o:w_ogilvie|William Ogilvie (1846 - 1912)]]
  *[[o:a_ogilvy|Alexander Cameron Ogilvy (1930 - 2015)]]
  *[[o:j_ogilvy|Jan Ogilvy (1936 – 2024)]]
  *[[o:j_oglow|“Apple Jimmy” Oglow (1867 – 1941)]]
  *[[o:k_oharra|Kenneth O'Harra]]
  *[[o:y_okada|Yoneda Okada (d. 1928)]]
  *[[o:d_okeefe|Dorothy O'Keefe, nee Ogburn]]
  *[[o:p_olafson|Peter Olafson]]
  *[[o:o_crow|Old Crow, Zzeh Gittlit  / Deetru' K'avihdik (early 1800s - 1869)]]
  *[[o:f_oles|Frances Oles]]
  *[[o:a_oleson|Andrew Oleson]]
  *[[o:w_olive|W.H.T. Olive (1865 - 1940)]]
  *[[o:l_olsen|Lawrence Olsen (d. 1899)]]
  *[[o:p_olsen|Pete Olsen]]
  *[[o:j_olson|Jackie Olson]]
  *[[o:jo_olson|John Olson (1930 – 2020)]]
  *[[o:r_olson|Robert Olson (1940 - 2004)]]
  *[[o:m_olson|Marline Yeiko Olson, nee Tamagi (1912 - 1999)]]
  *[[o:l_olynyk|Lee Olynyk]]
  *[[o:a_omeara|Arthur Eugene O’Meara (1859 - 1928)]]
  *[[o:e_oneill|Emerson O’Neill (d. ~1921)]]
  *[[o:j_oneill|John Arthur William O’Neill (b. 1880)]]
  *[[o:jo_oneill|John R. O’Neill]]
  *[[o:b_oneill|J. Barry O’Neill (d. 1999)]]
  *[[o:d_ordish|David Arthur Ordish (1943 – 2024)]]
  *[[o:h_ornstein|Honora “Diamond Lil” Ornstein (1883 - 1975)]]
  *[[o:m_oros|Michael “Shesley Free Mike” Oros (1952 -1985)]]
  *[[o:g_ortell|George Ortell (1872 - 1943)]]
  *[[o:m_orourke|Michael James “Mickey” O’Rourke (1878 – 1957)]]
  *[[o:e_orr|Edward S. Orr (1854 - 1926)]]
  *[[o:f_osborn|Franklin Herman Osborn (1867 – 1941)]]
  *[[o:h_osborn|Harriett Edna Osborn, nee Haines (1872 – 1965)]]
  *[[o:f_osborne|Frank H. Osbourne]]
  *[[o:j_ostashek|John Ostashek (1936 - 2007)]]
  *[[o:a_oster|Al Oster (1925 - 2017)]]
  *[[o:b_oster|Bill Oster (b. 1967)]]
  *[[o:k_ostrom|Kathyrn "Katie" Lorraine Ostrom (1943 - 2013)]]
  *[[o:g_otis|George Eric Otis (1872 - 1917)]]