Robert O'Brien may refer to:
Sportspeople Robert O'Brien (cricketer) (1869–1922), Australian cricketer Robert O'Brien (racing driver) (1908–1987), American racing driver Bob O'Brien (basketball) (1927–2008), American basketball player Robert O'Brien (canoeist) (born 1933), American sprint canoer Bob O'Brien (baseball) (born 1949), baseball player
Others Robert J. O'Brien (1858–1948), American real estate developer, politician and philanthropist Robert O'Brien (executive) (1907–1997), American businessman Robert C. O'Brien (author) (1918–1973), American journalist and children's book author Robert O'Brien (1918–2005), film and TV writer, most notably Say One for Me (1959) Robert O'Brien (artist) (born 1939), British Hong Kong artist Robert O'Brien (RAF officer) (active in 1990s), former US Air Secretary Robert C. O'Brien (born 1966), US National Security Advisor