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. * Francis O'Beirne * Sir Bill O'Brien (1983–2005) * Cornelius O'Brien * Sir Edward O'Brien, 4th Baronet * J. F. X. O'Brien * James O'Brien * John O'Brien * Lucius O'Brien, 13th Baron Inchiquin * Mike O'Brien (1992–2010) * Patrick O'Brien * Stephen O'Brien (1999–2015) * William O'Brien * William Smith O'Brien * Charles O'Connell * Daniel O'Connell * Daniel O'Connell Jnr * John O'Connell * Maurice O'Connell * Art O'Connor * Arthur O'Connor * Feargus O'Connor * John O'Connor * John O'Connor * Morgan John O'Connell * T. P. O'Connor (1880–1929) * James Edward O'Doherty * Jos