List of United Kingdom MPs: O

Following is an incomplete list of past and present Members of Parliament (MPs) of the United Kingdom whose surnames begin with O. The dates in parentheses are the periods for which they were MPs.

• Bill O'Brien (1983–2005)
• Mike O'Brien (1992–2010)
• Stephen O'Brien (1999–2015)
• T. P. O'Connor (1880–1929)
• Charles James O'Donnell (1906–1910)
• Edward O'Hara (1990–2010)
• Martin O'Neill, Baron O'Neill of Clackmannan (1979–2005)
• Gordon Oakes (1964–1997)
• Mark Oaten (1997–2010)
• William Oldfield (1942–1955)
• Laurence Oliphant (1865–1869)
• Bill Olner (1992–2010)
• Sarah Olney (2016–2017)
• Richard Onslow, 1st Baron Onslow (1679–1715)
• Chi Onwurah (2010–present)
• Lembit Öpik (1997–2010)
• Sally Oppenheim-Barnes, Baroness Oppenheim-Barnes (1970–1987)
• Diana Organ (1997–2005)
• William Ormsby-Gore, 4th Baron Harlech (1910–1938)
• William David Ormsby-Gore, 5th Baron Harlech (1950–1961)
• William Ormsby-Gore, 2nd Baron Harlech (1841–1852), (1858–1876)
• George Osborne (2001–present)
• Sandra Osborne (1997–present)
• Richard Ottaway (1983–1987), (1992–2015)
• Albert Owen (2001–present)
• David Owen (1966–1992)
• Idris Owen (1970–1974)