|Count of Flanders|
|Reign||988 – 1035|
|Died||30 May 1035|
|Spouse(s)||Ogive of Luxembourg|
Eleanor of Normandy
|Issue||Baldwin V, Count of Flanders|
Judith of Flanders, Countess of Northumbria
|Father||Arnulf II, Count of Flanders|
|Mother||Rozala of Italy|
Baldwin IV was the son of Count Arnulf II of Flanders (c. 961 — 987) and Rozala of Italy (950/60 – 1003), of the House of Ivrea. He succeeded his father as Count of Flanders in 987, but with his mother Rozala as the regent until his majority.
In contrast to his predecessors Baldwin turned his attention eastward, leaving the southern part of his territory in the hands of his vassals the counts of Guînes, Hesdin, and St. Pol. To the north of the county Baldwin was given Zeeland as a fief by the Holy Roman Emperor Henry II, while on the right bank of the Scheldt river he received Valenciennes (1013) and parts of the Cambresis as well as Saint-Omer and the northern Ternois (1020). In his French territories, the supremacy of the Baldwin remained unchallenged. A great deal of colonization of marshland was organized along the coastline of Flanders and the harbour and city of Brugge were enlarged.
Baldwin first married Ogive, daughter of Frederick of Luxembourg, by whom he had a son and heir, Baldwin V (1012 – 1067). He later married Eleanor, daughter of Richard II of Normandy, by whom he had a daughter, Judith (1033 – 1094). Baldwin IV died on 30 May 1035.
- John E. Morby, "The Sobriquets of Medieval European Princes", Canadian Journal of History, 13:1 (1978), p. 9. Baldwin called himself Honesta Barba (true beard) in his own charters.
- Detlev Schwennicke, Europäische Stammtafeln: Stammtafeln zur Geschichte der Europäischen Staaten, Neue Folge, Band II (Marburg, Germany: J. A. Stargardt, 1984), Tafel 5
- Jean Dunbabin. France in the Making 843-1180, Second Edition (Oxford; New York; Oxford University Press, 2004), p. 208
- Heather J Tanner, Families, Friends, and Allies: Boulogne and Politics in Northern France and England c. 879–1160 (Leiden; Boston: Brill, 2004), pp. 73, 75-6, 77–8
- Douglas Richardson, Royal Ancestry: A Study in Colonial and Medieval Families, Vol.V, Royal Ancestry Series, Salt Lake City, Utah (2013), p. 497
- Philip Grierson, 'The Relations between England and Flanders before the Norman Conquest', Transactions of the Royal Historical Society, Vol. 23 (1941), pp. 109-110