- O'Brien, Chistopher (1)
- O'Brien, Christopher (10)
- O'Brien, Dr. William A. (2)
- O'Brien, Dr. William Jr. (1)
- O'Brien, Jean (4)
- O'Brien, William A. (1)
- O'Brien, William Austin (1)
- O'Bryant, Beverly J. (president, American Counseling Association) (1)
- O'Callaghan, E. B. (Edmund Bailey), 1797-1880 (2)
- O'Connell, Brian (1)
- O'Connell, Jodell (community health specialist, Hennepin County Community Health Department) (1)
- O'Conner, William Van (2)
- O'Connor, James (1)
- O'Connor, Kathy (1)
- O'Donnell, Kathleen (1)
- O'Fallon, David (2)
- O'Hare, Daniel (7)
- O'Kane, T. C. (Tullius Clinton), 1830-1912 (4)
- O'Kane, T. C.(Tullius Clinton), 1830-1912. (2)
- O'Meara, James (1)
