Baldwin IV of Flanders (died May 30, 1036), known as the Bearded, was Count of Flanders from 988 to 1036.

He was the son of Arnulf II of Flanders.

Baldwin turned his attentions to the east and north, leaving the southern part of his territory in the hands of his vassals the counts of Guines, Hesdin, and St. Pol.

To the east was Lotharingia, and here Baldwin took Valenciennes, the Cambresis, and Hainaut. It was not until 1056, during the minority of the Emperor Henry IV, then he fully secured this territory, which was then recognized as fier held of the emperor.

In the more central and northerly parts of Flanders, the count's supremacy was unchallenged. Here there was a great deal of internal reclamation and colonization of marshland, all of which belonged to the counts of Flanders.

Baldwin first married Ogive of Luxemburg, and was succeeded by their son Baldwin V. He later married Eleanor of Normandy, daughter of Richard II of Normandy, by whom he had a daughter Judith. She married first Tostig Godwinson, Earl of Northumberland, and then Duke Welf of Bavaria. These widespread family connections demonstrate the political interests of the Flemish counts, both in England to the west and in Germany to the east.