John I, Count of Hainaut

John I of Avesnes (May 1 1218 – December 24 1257) was count of Hainaut from 1246 to his death. John was son of Countess Margaret II of Flanders and Hainaut as Margaret I, by her first husband, Count Bouchard IV of Avesnes. He inherited Hainaut, during Margaret's lifetime, while his half brother Guy of Dampierre became Count of Flanders. He married Adelaide of Holland in 1246 and had the following issue:

• John II, Count of Hainaut and Holland (1247–1304)
• Joanna, abbess of Flines (died 1304)
• Bouchard, Bishop of Metz (1251–1296)
• Guy, Bishop of Utrecht (1253–1317)
• William, Bishop of Cambrai (1254–1296)
• Floris, stadholder of Zeeland and Prince of Achaea

See also: Counts of Hainaut family tree