Family name Ó Riain (Ó Riain 
) , around the globe, is a very rare last name. The surname Ó Riain is habitual in Northern Europe, particularly Ireland, where it is quite a rare surname.
| VARIANT | COUNTRY |
|---|---|
| Ó Riain | Ireland |
| art ó riain Irish writer and civil servant (1893-1968), IE (b. 1893) |
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seán ó riain IE (b. 1955) |
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| séamus ó riain Irish hurler, Gaelic footballer and Gaelic games administrator (1916-2007), IE (b. 1916) |
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| pádraig ó riain Irish linguist, IE (b. 1939) |
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| seán ó riain (b. 1968) |
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| hildegard ó riain Irish diplomat, IE |
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