Piter De Vries is a fictional character from Frank Herbert's Dune science fiction series.

He is a "twisted" mentat in the service of Baron Vladimir Harkonnen. His "twisted" nature is obvious, most notably in him being a sadist and acting as a torturer for the Baron. Generally regarded as architect of the plan to destroy the Harkonnen's long time enemy, House Atreides, while returning the Baron's stewardship over Arrakis. De Vries is unusual in that despite his near-prescient mental abilities and intelligence, he serves the Baron with great enthusiasm knowing that one day his master plans on killing him. Piter was killed on Arrakis shortly after House Harkonnen's troops and Imperial Sardaukar had captured Duke Leto Atreides. He was assassinated by Leto, who had been given a false tooth by Wellington Yueh, the Suk doctor who betrayed House Atreides. When the tooth was crushed, a poisonous gas emerged from inside. The attack was meant to kill the Baron, but failed.