Brían Francis O'Byrne (born 16 May 1967) is an Irish actor who works and lives in the United States. He was nominated for a Primetime Emmy Award for his role in the miniseries Mildred Pierce (2011) and won a BAFTA TV Award for his role in the drama series Little Boy Blue (2017).

O'Byrne received five Tony Award nominations and won Best Featured Actor in a Play for his performance in the 2004 production of Frozen.

Early life and education
O'Byrne was born in Mullagh, a village in the south-east of County Cavan, on 16 May 1967. He attended the Samuel Beckett Centre at Trinity College (T.C.D.) in Dublin. He moved to New York City in 1990, and was cast in the Irish Repertory Theatre production of Philadelphia, Here I Come!