William Douglas-Hamilton, Duke of Hamilton, KG, PC (24 December 1634 – 18 April 1694), also known as Lord William Douglas and the Earl of Selkirk, was a Scottish nobleman and politician. He was the eldest son of The 1st Marquess of Douglas by his second wife, Lady Mary Gordon, a daughter of The 1st Marquess of Huntly. Subsequent to marrying Anne Hamilton, 3rd Duchess of Hamilton, he was created Duke of Hamilton in the Peerage of Scotland, which also allowed him to use his wife's subsidiary titles during his lifetime and to take the name Hamilton for their descendants.