Ranulf I (also Ramnulf, Rannulf, and Ranulph) (820–866) was a Count of Poitiers (from 835) and Duke of Aquitaine (from 852). He is considered a possible son of Gerard, Count of Auvergne, and Hildegard (or Matilda), daughter of Louis the Pious and Ermengard. Few details are known about Ranulf I, except that he died in 866 in Aquitaine from wounds received in the Battle of Brissarthe against the Vikings (in which Robert the Strong also died). Ranulf I is a 32x great-grandfather of Elizabeth II, as well as being an ancestor of many people of European descent.