Joan, often called Joan of Constantinople, was the countess of Flanders and Hainaut from 1205 until her death. She was the elder daughter of Baldwin IX, Count of Flanders and Hainaut, and Marie of Champagne.
- Occupation
- politician
- Position held
- Count of Flanders, count of Hainaut
- Born
- 1200
- Died
- December 5, 1244, 1244
