was built by John de Courcy, a Norman knight, who invaded Ulidia (Ulster) in 1177 and took control. Originally a large portion of the castle jutted out into the sea in Belfast Lough providing excellent defense against attack. In 1204 Another Norman knight
by the name of Hugh de Lacy defeated John de Courcy and took control of his lands and the castle at Carrickfergus. Hugh continued the building work at the castle including the construction of the great four-storey square keep and further curtains walls. The castle changed ownership again when King John of England laid siege
to it and captured it in 1210. After King John's departure a constable
was appoined to administer the castle and money was provided for repairs.
In 1315 Ireland was invaded by Edward Bruce and the town of Carrickfergus was captured. But the castle was only taken after a year-long siege.