Surname O'Regan (O'Regan 
) , all around the world, is quite a rare cognomen. The cognomen O'Regan is characteristic of Ireland, where it is quite a common surname, Australia, where it is quite a rare surname, and New Zealand. In absolute terms, it is commonest in Ireland, Australia, and the United Kingdom.
| VARIANT | COUNTRY |
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| O'Regan | Australia, Canada, Ireland, United Kingdom, United States |
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anthony o'regan Catholic bishop, GB (b. 1809) |
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patrick o'regan New Zealand politician, NZ (b. 1869) |
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| michael o'regan United States Army Medal of Honor recipient, US (b. 1846) |
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| mary anne o'regan (born 1846) (b. 1846) |
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william v. o'regan American Navy admiral, US (b. 1900) |
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rolland o'regan New Zealand surgeon, activist and politician, NZ (b. 1904) |
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| john o'regan Australian politician (1877-1940) (b. 1877) |
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tipene o'regan New Zealand businessman and academic, NZ (b. 1939) |
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| jim o'regan Irish hurler and Gaelic footballer, IE (b. 1901) |
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| kathleen o'regan Irish actress (1903-1970), IE (b. 1903) |
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mark o'regan New Zealand lawyer and jurist, NZ (b. 1953) |
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| ern o'regan Australian rules footballer (1907-1996), AU (b. 1907) |
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| barry o'regan New Zealand jurist (1915-1995), NZ (b. 1915) |
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| bobby o'regan Irish hurler (b. 1920) |
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seamus o'regan Canadian broadcast journalist, CA (b. 1971) |
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