| Robert I | |
|---|---|
 Seal of Robert I | |
| Count of Flanders | |
| Reign | 1071–1093 |
| Predecessor | Arnulf III |
| Successor | Robert II |
| Born | c. 1035 |
| Died | 13 October 1093 (aged 57–58) |
| Spouse | Gertrude of Saxony |
| Issue | |
| House | House of Flanders |
| Father | Baldwin V of Flanders |
| Mother | Adela of France |
Robert I (c. 1035 – 13 October 1093), known as Robert the Frisian, was count of Flanders from 1071 until his death in 1093. He was a son of Baldwin V, Count of Flanders, and the younger brother of Baldwin VI, Count of Flanders. He usurped the countship after defeating his nephew Arnulf III and his allies, which included King Philip I of France, Count Eustace of Boulogne and the counts of Saint-Pol and Ardres at the Battle of Cassel.[1] He subsequently made peace with Philip, who became his stepson-in-law, but remained hostile to his sister Matilda and her husband William the Conqueror, who was king of England and duke of Normandy.
- ^ Charles Verlinden, Robert Ier le Frisson, Ghent, 1935.