Lawrence Francis "Larry" O'Brien, Jr. (July 7, 1917 – September 28, 1990) was one of the United States Democratic Party's leading electoral strategists when, for more than two decades, he helped reshape American politics. He served as Postmaster General in the cabinet of President Lyndon Johnson.

He also served as Commissioner of the National Basketball Association from 1975 to 1984.

O'Brien, son of Irish immigrants, was born in Springfield, Massachusetts. When he wasn't working in politics, O'Brien managed his family's real estate and did public relations work as well.