During which king's reign did Newton become Warden of the Mint in 1696?

Newton became Warden of the Mint in 1696 during the reign of King William III. The appointment moved him from Cambridge academic life into a major government role in London.

Newton obtained the position through the influence of Charles Montagu, Chancellor of the Exchequer and a political supporter. The Royal Mint was then preparing for the Great Recoinage, a large effort to replace worn and clipped silver coins and restore confidence in England’s currency.

The office was not merely ceremonial for Newton. He investigated counterfeiting, questioned suspects and witnesses, and pursued prosecutions. In 1699, he advanced from Warden to Master of the Mint, a position he held for the rest of his life. A common mix-up is to associate the appointment with Queen Anne, but she did not begin her reign until 1702; William III was king in 1696.