Duke Baldwin IV of Flanders, also known as Baldwin IV of Hainaut, was a medieval noble who ruled from 1171 to 1186. He was a member of the House of Flanders and played a significant role in the politics of the region during the 12th century. Baldwin IV was known for his efforts to strengthen the power of his duchy and for his involvement in the Crusades, which aimed to reclaim the Holy Land. Baldwin IV was the son of Baldwin III of Hainaut and Margaret I of Flanders. His reign was marked by conflicts with neighboring territories and internal struggles for power. Despite these challenges, he is remembered for his contributions to the development of Flanders and his efforts to maintain its independence during a tumultuous period in European history.