Callahan

Callahan is a surname of Irish origin, anglicized from the Gaelic Ó Ceallacháin, meaning "descendant of Ceallachán," with Ceallachán a personal name derived from Ceallach. The name is widespread in Ireland and among the Irish diaspora, particularly in the United States, Canada, and Australia. Variants of the name include Callaghan, O'Callaghan, and O'Callaghan; in some families, Callahan is a shortened form.

In addition to its use as a surname, Callahan appears in place names and popular culture. Place names named Callahan are found in several countries, especially in North America, where communities bearing the name exist as small towns or unincorporated areas. In fiction, Callahan's Crosstime Saloon is a notable work by Spider Robinson, set in a bar named Callahan's that serves as a nexus for time-travel stories and humorous debates among its patrons.

Notable individuals with the surname include politicians, athletes, writers, and scientists, reflecting the surname's broad distribution. However, no single figure defines the name.

Related surnames include Callaghan and O'Callaghan, which share the same Gaelic origin.