Isaac Newton, renowned for his laws of motion and universal gravitation, also served as Warden and then Master of the Royal Mint. Appointed to the position in the late 17th century, Newton unexpectedly found himself leading a crackdown on widespread counterfeiting. The problem of forged currency was rampant in England at the time, posing a significant threat to the nation’s economy. Newton applied his scientific rigor to the investigation of counterfeiters, modernizing the mint’s processes and pursuing legal action against those involved. He personally oversaw prosecutions, securing convictions and contributing to a significant reduction in the circulation of fake coins. This lesser-known chapter reveals Newton’s dedication to public service and his surprising aptitude for financial detective work, effectively saving the British Treasury.