O'Sullivan
An Irish surname meaning “descendant of Súlbhán,” tied to one of the great Gaelic dynastic names of Munster.
The #3,032 most common surname in the United States (2010 Census) — about 1 in every 26,125 Americans shares it.
Etymology
O'Sullivan comes from Irish Gaelic Ó Súilleabháin, meaning “descendant of Súilleabhán.” The personal name is usually explained as a form built from súil, “eye,” though the exact development of the name is historically debated. In practice, it is a hereditary Gaelic family name rather than a simple descriptive nickname.
History
The name is famously associated with the O'Sullivan clans of southwest Ireland, especially County Cork and County Kerry. After English-language spelling became common, the apostrophe form O'Sullivan became standard, though older records often show variants without it. Like many Irish surnames, it spread widely through emigration in the 19th and 20th centuries.
Origin
Regions
Variant spellings
Fun fact
Sullivan is one of the most recognizable Irish surnames in the English-speaking world, and the O' form preserves the older Gaelic prefix ó, meaning “descendant of.”