Murtogh O'Brien (c. 1545 – 30 April 1613) was an Anglican bishop of Killaloe, in County Clare, Ireland.
He was of a branch of the clan O'Brien known as O'Brien-Arra, from County Tipperary.
He was educated in England at Magdalene College, Cambridge, and became an Anglican priest.
On 15 May 1570, he was appointed Protestant Bishop of Killaloe by Elizabeth I; however, he was not consecrated until six years later.
[1] Even before his appointment, because of his family's position of power in the kingdom of Thomond, O'Brien received all of the profits from that see.