William O'Brien (disambiguation)
William O'Brien is the name of:
- William O'Brien, 4th Earl of Inchiquin ( 1700-1777 ), Irish politician
- William O'Brien (1852-1928), Irish politician
- William O'Brien ( Admiral ) (* 1916), British admiral
- William O'Brien (1918-1994), Irish politician
- William David O'Brien (1878-1962), American clergyman, Auxiliary Bishop of Chicago
- William J. O'Brien (1836-1905), American politician
- William L. O'Brien ( born 1951 ), American lawyer and politician
- William Smith O'Brien ( Ireland) ( 1803-1864 ), Irish politician
- William Smith O'Brien (West Virginia ) ( 1862-1948 ), American politician
- William X. O'Brien (1881-1968), Irish politician
- Disambiguation