Margaret of York, Duchess of Burgundy (3 May 1446 – 23 November 1503) – also known as Margaret of Burgundy by marriage – was a daughter of Richard Plantagenet, 3rd Duke of York and Cecily Neville. Secretly a member of the Templar Order, Margaret managed to gather much Yorkist support opposing the ruling House of Tudor.
Margaret of York took a leading role in the Yorkist Templar plot to overthrow King Henry VII. The Templars manipulated the young Lambert Simnel into pretending to the Earl of Warwick, and later assigned Perkin Warbeck to pretend to be Richard of Shrewsbury, 1st Duke of York, both individuals with claims to the throne. Henry VII thwarted each attempt, imprisoning Simnel and hanging Warbeck.
King Henry was aware of Margaret's involvement in the plot, but took no action against her due to her ties to Maximilian I, the Holy Roman Emperor. In 1503, members of the Assassin Brotherhood offered to eliminate Margaret, on conditions that she died "naturally". The Assassins poisoned her food, face paint and pillow separately to avoid exposing the plot, and Margaret died from the poison on 23 November 1503.