Eliza Oneil to Fredrick Oram - 1881 Census household returns
- Eliza Oneil to Michael Oneil
- Michael Oneil to Michael Oneill
- Michael Oneill to John Ong
- John Ong to Edward Ongley
- Elizabeth Ongley to Jeremiah Oniel
- John Oniel to Hannah Onion
- Harley Onion to Joseph Onion
- Joseph R Onion to William Onion
- William Onion to Benjamin Onions
- Benjamin Onions to Edwin Onions
- Edwin Onions to Henry Onions
- Henry Onions to James Onions
- James Onions to John Onions
- John Onions to Joseph T Onions
- Josephus Onions to Simon Onions
- Stephen Onions to William Onions
- William Onions to George Onley
- Harvey Onley to Henry Onn
- John Onn to Edward Onslow
- Edward Onslow to Pitcairn Onslow
- Richard Onslow to William Onwin
- James Ony to Rachael Opbaldestar
- Albartus Opbroek to David Openshaw
- David Openshaw to Harriet Openshaw
- Henery Openshaw to James Openshaw
- James Openshaw to John Openshaw
- John Openshaw to Margaret Openshaw
- Margaret Openshaw to Samuel Openshaw
- Samuel Openshaw to William Openshaw
- William Openshaw to Thomas Opher
- William Opher to Ernest Opie
- Evelina Opie to John Opie
- John Opie to Nicholas Opie
- P J Opie to William J Opie
- William Richard Opie to David Oppenheimer
- Herman Oppenheimer to Thomas Oppy
- Thomas Oppy to Albert Oram
- Albert Oram to Charles Oram
- Charles Oram to Edward E Oram
- Edward G J Oram to Fredrick Oram