Sir Brian O'Rourke (Irish: Brian na Múrtha Ó Ruairc) (c. 1540 – 1591) was firstly king, then lord, of West Breifne in Ireland from 1566 until his execution in 1591. He reigned during the later stages of the Tudor conquest of Ireland and his rule was marked by English encroachments on his lands. Despite being knighted by the English in 1567, he would later be proclaimed a rebel and forced to flee his kingdom in 1590. He travelled to Scotland in early 1591 seeking assistance from King James VI, however he was to become the first man extradited within Britain on allegations of crimes committed in Ireland and was sentenced to death in London in November 1591.