Philip de Montmorency was also known as Count of Hoorn.

He was a stadtholder of Guelders and an admiral of Flanders. He was a knight of the Golden Fleece.

In 1559 he commanded the stately fleet which conveyed Philip II from the Netherlands to Spain, and he remained at the Spanish court untill 1563. On his return he placed himself with the Prince of Orange and Count of Egmont at the head of the party which opposed the policy of Cardinal Granvelle. When Granvella retired the three nobles continued to resist the introduction of the Spanish Inquisition and of Spanish despotic rule into the Netherlands.

Together with the Count of Egmont he was seized, tried and condemned as traitor. They were executed on the June 5, 1568 in the great square before the town hall at Brussels.