Eustace I, Count of Boulogne, was a nobleman in the 11th century, known for his role in the early development of the County of Boulogne in France. He was the son of Eustace I of Boulogne and became a prominent figure in the region, contributing to the political landscape of medieval Europe. Eustace I was also involved in the First Crusade, which began in 1096. He was a supporter of the Crusader movement, which aimed to reclaim the Holy Land. His legacy includes the establishment of the Eustachian lineage, which played a significant role in the history of the region.