O'Callaghan is a surname of Irish origin, commonly found in Ireland and among Irish communities worldwide. It is derived from the Gaelic name Ó Ceallacháin, which means "descendant of Ceallach," a personal name that may mean "bright-headed" or "warrior." The name is often associated with various historical figures and families in Ireland. In addition to being a surname, O'Callaghan can refer to several places and institutions, such as O'Callaghan Park in Ireland or O'Callaghan Hotels, a hospitality group. The name is also linked to notable individuals, including John O'Callaghan, a musician known for his work in the alternative rock genre.