William Piers (c. 1510 – 1603) was an English constable, who spent most of his life in Ireland. He was the first mayor and practical founder of Carrickfergus. He was noted in particular for his attempts to drive out the Scots from Ulster and the great lengths that he went to in attempting to enhance the power of local chiefs at the expense of the Scots. Granted Tristernagh Abbey as a reward for his military services, he made it into his family home from the late 1560s until his death in 1603.