Diederik Sonoy or Snoey (Kalkar, Duchy of Cleves, 1529 – Pieterburen, 2 June 1597) was a leader of the Geuzen during the Eighty Years' War.

He early entered military life, signed the compromise of Nobles, and was one of the most fierce advocates of the interests of the Prince of Orange.

He was provided by William the Silent with a commission, appointing him Lieutenant-Governor of North Holland or Waterland.

When he was discharged and received a pension he and his family crossed over to England, where he endeavoured to drain some land granted him by Elizabeth I; but failing he returned (1593) to East Frisia, resided for some time at Norden, and died 2 June 1597 on his seat near Pieterburen.

[2] Engelbert Terburg, a lay brother of the same monastery, was transferred by Sonoy to the village of Ransdorp, near Amsterdam, where he was hanged on 11 August 1572 after being subjected to torture.