OShaughnessy

O'Shaughnessy, often written with an apostrophe as O'Shaughnessy, is an Irish surname derived from the Gaelic Ó Seachnasaigh, meaning "descendant of Seachnasach." The name originates from medieval Gaelic Ireland and was historically associated with families in Connacht, particularly in the western counties. As with many Irish surnames, its bearers spread beyond Ireland through migration to Britain, North America, and other parts of the world, contributing to a wide diaspora.

Variants and spellings vary. The name is commonly anglicized as O'Shaughnessy or Shaughnessy, with other historical forms including Seachnasaigh and Seachnasagh appearing in older records. The form OShaughnessy (without an apostrophe) is frequently used in modern contexts, especially in the United States and elsewhere where the apostrophe is not standard.

Notable people with the surname have made contributions across fields such as politics, science, arts, and sports; however, individual entries vary and readers are encouraged to consult specific biographical sources for detailed information. The name also appears in place names and institutions, reflecting the historical footprint of families bearing the Ó Seachnasaigh lineage.