Eustace I Count of Boulogne

Eustace I, Count of Boulogne (1024–1047), was a prominent nobleman and founder of the Boulogne branch of the House of Flanders. He succeeded his father, Baldwin II, as count of Boulogne in 1024 and also held the county of Lens. In 1028, he confirmed the foundation of a college of canons at his castle in Lens, which remained under his control until his death when it was passed to his son Lambert.

Eustace operated independently from Flanders during the minority of Baldwin IV and later worked with Baldwin V of Flanders on various ventures, including limiting the powers of abbey officials like the Abbey of Saint Bertin. He allied with the Normandy ducal house through the marriage of his son Eustace II to Goda, niece of Richard II of Normandy, which established connections with other notable families, including that of England's King Edward the Confessor.

Eustace I was a patron of Samer Abbey near Calais and was buried there. He married Matilda of Louvain, daughter of Lambert I of Louvain, and had several children: Eustace II of Boulogne, Godfrey (Bishop of Paris from 1061 to 1095), Lambert II, Count of Lens, and Gerberga, who married Frederick, Duke of Lower Lorraine. His reign marked the rise of the Counts of Boulogne in northern France.

Under Eustace I, the House of Boulogne gained significant prominence through strategic alliances and independent governance, leaving a lasting legacy in medieval Europe.