Sir William Waad (also Wade or Wadd) (1546 - 1623) was an English diplomat and administrator. He served as a special diplomatic agent for Elizabeth I of England. She sent him to France to collect papers which were used to convict her sister, Queen Mary. Waad also carried out the questioning and interrogations of political prisoners, often using torture to get the answers. He was involved in questioning Sir Walter Raleigh, members of the Gunpowder Plot, and the Essex rebellion among others.