William Herle (died 1589[1]) was an Englishman who was both a Member of Parliament and the county sheriff; he was also a privateer and spy while imprisoned in the Marshalsea prison in 1571. He became known for his part in Elizabeth I's intelligence network inside the jail. He smuggled letters from William Cecil and Lord Burghley about people involved in the so-called Ridolfi plot, which was a Roman Catholic plan to assassinate the Queen and replace her with Mary, Queen of Scots.[2]