Lucius O'Brien may refer to:

Lucius O'Brien (died 1717) Sir Lucius O'Brien, 3rd Baronet (1731–1795), Member of the Parliament of Ireland Lucius O'Brien, 13th Baron Inchiquin (1800–1872), Irish politician and nobleman Lucius O'Brien, 15th Baron Inchiquin (1864–1929) Lucius Richard O'Brien (1832–1899), Canadian painter Lucius O'Brien (priest) (1842–1913), Dean of Limerick in the Church of Ireland