Reilly (pronunciation: /ˈraɪli/) is an Irish surname (other forms include O'Reilly and ), and is derived from the Gaelic Ó Raghallaigh Sept that was based in Counties Cavan and Westmeath. Reilly is among the ten most frequently found surnames in Ireland and although they are very widespread they can be mostly found in the region of the ancestral homeland.
People with the surname Reilly include: