O'Reilly: Last Name Origin and Family Crest

Behind the O'Reilly surname stands Reilly, an Irish name that clerks and families wrote in more than one way. The name is usually explained as “Descendant of Raghallach”.

• O'Reilly simply joins the particle O' to Reilly, a pattern common in Irish naming.
• You may also find the name written Riley and Ryley.

O'Reilly coat of arms

Arms linked to Reilly and its spellings were granted to individual families; our heraldry team traces which line they belonged to. Get the complete O'Reilly report, with a museum-style coat of arms.