Robert I ( – 13 October 1093), known as Robert the Frisian, was count of Flanders from 1071 until his death in 1093. He was a son of Count Baldwin V out of his first marriage, He was the older brother of Count Baldwin VI and claimed the countship after defeating his nephew Arnulf III and his allies, which included King Philip I of France, Count Eustace II of Boulogne and the counts of Saint-Pol and Ardres at the Battle of Cassel. 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.
Early life
Robert was the older son of Baldwin V of Flanders and an unknown wife. His younger brother, Baldwin VI, succeeded their father as count of Flanders in 1067. His sister Matilda married in 1051/2 William the Conqueror, duke of Normandy and later king of England. His nickname 'the Frisian' was obtained, apparently, when he acted as regent for his stepson, Count Dirk V of Holland Adela († 1115), who became queen of Denmark, The second was made at Bruges (1069/70) in the presence of his brother Baldwin VI. while Richilde, Arnulf's mother, was to be regent until Arnulf came of age.
Count of Flanders
Despite the oath, Robert disputed the succession of his nephew Arnulf III upon Baldwin VI's death. He recruited supporters in the Maritime Flanders and Ghent, and finally entered the latter with the intent of taking Flanders for himself. Robert refused and continued his war with Richilde at which point Philip I amassed an army which he brought to Flanders. Among his allies were the counts of Boulogne, Saint-Pol and Ardres.) and William FitzOsborn. As a part of their negotiations Corbie, an important trade center, which had been ceded by Arnulf III in order to secure the king's help, was returned to royal control. and William's rebellious son Robert Curthose in 1078/79. In 1075, Robert let the Danish fleet of king Sweyn II of Denmark use Flanders harbors in their intended expedition against England. However, the rebellion of Canute's brother Olaf delayed the expedition, and finally Canute's assassination put a definitive end to the plan. The victory changed the course of the hostilities, allowing Dirk and future counts to reconquer the territories of the county of Holland they had lost in the past.
During the papacy of Urban II the Flemish clergy complained about the exactions imposed by Robert at a provincial council in Rheims (around 1092). A delegation composed of Arnulf (provost of Saint Omer), Jean (abbot of Saint Bertin), Gerard (abbot of Ham) and Bernard (provost of Watten) threatened Robert with an interdict in case the exactions did not end. Robert complied and returned the goods he had confiscated. In one battle Robert and three of his companions rode ahead of the main army charging the forces under the command of Kerbogha, whose forces the Christians scattered completely. Robert died <!--where?-->13 October 1093.