O'Brien may refer to:
People O'Brien (surname), an Irish surname O'Brien dynasty, a powerful Irish dynasty that ruled Munster and produced several High Kings of Ireland
Places United States O'Brien, California, an unincorporated community in Shasta County O'Brien, Florida, an unincorporated community in Suwannee County O'Brien, Oregon, a census-designated place and unincorporated community in Josephine County O'Brien, Texas, a city in Haskell County O'Brien County, Iowa, a county
Other places O'Brien, Argentina, a town in Buenos Aires Province, Argentina O'Briens Hill, Queensland, a locality in the Cassowary Coast Region, Australia O'Brien Island, in the South Shetland Islands, Antarctica O'Brien Island, Chile, in the Magallanes Region, Chile
Ships USS O'Brien, a list of ships with this name Capitan O'Brien-class submarine three submarines built for the Chilean Navy in 1928–1929 Oberon-class submarine (also known as O'Brien-class submarine), Chilean Navy submarine class Chilean submarine O'Brien (S22), an Oberon-class sub
Other uses O'Brien (Nineteen Eighty-Four), the main antagonist in George Orwell's novel O'Brien (TV series), a British talk show presented by James O'Brien United States v. O'Brien, legal case ruled on by the US Supreme Court regarding draft card burning and the First Amendment's guarantee of free speech O'Briens Irish Sandwich Bars, a café chain based in Ireland O'Brien AutoGlass, the Australian subsidiary of Belron.
See also Brien O'Brian, a surname (including a list of people with the name) O'Bryan (born 1961), American singer-songwriter Justice O'Brien (disambiguation)