Swedish statesman who served as King Charles XII's (Charles XII) leading minister during the Great Northern War (Northern War, Second) (1700–21).

Piper was of lesser noble background. He became an official in the Swedish chancellery's department of home affairs under King Charles XI but reached the heights of Swedish government in 1697, when the newly crowned Charles XII raised him to a countship and appointed him to the council of state.

Piper was the only high councillor to accompany Charles in the field during the Great Northern War. While he approved, along with the other field advisers, a decision to invade Russia, Piper later strongly opposed Charles's determination to remain there following early setbacks. He was captured during the Battle of Połtava (July 1709), and he remained a prisoner of the Russians until his death in 1716, despite Charles's repeated efforts to win his freedom through prisoner exchanges.