Murrough McDermot O'Brien (c.1550 - 20 April 1573) was the 3rd Baron Inchiquin. He was the son of Dermod O'Brien, 2nd Baron Inchiquin and Margaret O'Brien and inherited his title in 1557 on the death of his father.
He married Margaret Cusack, daughter of Sir Thomas Cusack of Cussington, Meath, Lord Chancellor of Ireland and his second wife Maud Darcy.
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