Henry I of Isenburg-Grenzau (1153 - 1222) was the Count of Isenburg-Grenzau from 1158 until 1220. Henry was a son of Count Gerlach of Isenburg-Limburg-Covern. After his father's death in 1258, Henry received his father's territories in the Lower Westerwald, while his brother Gerlach received those around Covern. Henry began the construction of the castle of Grenzau, which was completed around 1215. After his death in 1220, his lands were divided between his sons, Henry and Gerlach.