Margaret I of Flanders

Margaret of Alsace (c. 1145–1194), daughter of Count Thierry, inherited the county in 1191 after the childless death of her brother Philip of Alsace. In 1160 she married Ralph II of Vermandois, but his leprosy prevented the marriage from being consummated, and he died in 1167.

In 1169 she married Count Baldwin V of Hainaut, who ruled Flanders at her side. Their daughter Isabella married Philip II of France, while their sons Baldwin IX and Henry both became Latin emperors of Constantinople. Margaret ruled as countess suo jure until her death in 1194.