Last name О'Брайен (O'Brien 
, О'Брайен 
) , in the entire world, is a common surname. The surname О'Брайен is habitual in Ireland, where it is a common surname, Australia, where it is quite a common surname, and Jersey (explore the name in all countries). Not in comparison with a country's population, the name is most common in the United States, Australia, and Ireland. Much less frequently, О'Брайен is the forename as well as the last name.