O'Dea
| Language(s) | English, from Irish |
|---|---|
| Origin | |
| Derivation | Ó Deághaidh |
| Meaning | Descendant of Deághaidh (an Irish chieftain) |
| Region of origin | County Clare, Ireland |
O'Dea (/oʊˈdiː/ oh-DEE; Irish: Ó Deághaidh, formerly Ua Deághaidh), is an Irish surname derived from Deághaidh, the name of a tenth-century clan chieftain. According to historian C. Thomas Cairney, the O'Deas were one of the chiefly families of the Dal gCais or Dalcassians who were a tribe of the Erainn who were the second wave of Celts to settle in Ireland between about 500 and 100 BC.