The castle, from which the village takes its name, was first built in 1210 by knights under the leadership of Richard Earl de Clare, more commonly known as Strongbow. The original castle and its lands belonged to the Knights Templar following their foundation by Maurice Fitzgerald, the Earl of Desmond. This unique heritage is proudly displayed in the form of the Templar Cross, which forms the centrepiece of the resort's coat of arms.
Following rebellion in 1578, the Earl of Desmond James Fitzgerald's estates were forfeited to the crown. The lands were subsequently awarded to Sir Walter Raleigh whose fall from grace years later forced the sale of his beloved Castlemartyr to Richard Boyle, the first Earl of Cork. Castlemartyr remained in the hands of the Boyle family for over 300 years, during which time they commissioned the construction of the magnificent manor house.