Cornelius O'Brien may refer to:
- Cornelius O'Brien (piper) (fl. 1656), Irish musician
- Cornelius O'Brien (bishop) (1843–1906), Canadian Roman Catholic priest, archbishop, and author
- Cornelius O'Brien (County Clare) (1782–1857), politician and builder of O'Brien's tower
- Cornelius J. O'Brien (1869–1954), vaudeville and minstrel show performer
This disambiguation page lists articles about people with the same name.
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