Mac Giolla is a prefix-phrase used in some Irish surnames, meaning "son of the devotee of" (which is usually followed by the name of a prominent Christian saint). Examples of some notable individuals who bear this phrase in their surnames are:
Tomás Mac Giolla (1924–2010), former TD Antoine Mac Giolla Bhrighde (1957–1984), Provisional Irish Republican Army (IRA) volunteer Brian Mac Giolla Phádraig (c. 1580–c. 1652), Irish scholar and poet Cathal Buí Mac Giolla Ghunna (c. 1680–1756), Irish poet