Yolanda of Flanders ruled the Latin Empire in Constantinople for her husband Peter of Courtenay from 1217 to 1219.

She was the daughter of Baldwin V, Count of Hainault, and Countess Margaret I of Flanders. Two of her brothers, Baldwin I and then Henry, were emperors in Constaninople. After the death of the latter in 1216 there was a brief period without an emperor, before Peter was elected. Peter sent Yolanda to Constantinople while he fought the Despotate of Epirus, during which he was captured. Because his fate was unknown (although he was probably killed), Yolanda ruled as regent. She allied with the Bulgarians against the various Byzantine successor states, and was able to make peace with Theodore I Lascaris of the Empire of Nicaea, who married her daughter. However, she soon died, in 1219.

She was succeeded by her second son Robert of Courtenay because her first son did not want the throne. As Robert was still in France at the time, there was technically no emperor until he arrived in 1221.

Yolanda also held Namur, which she inherited from her uncle Philip of Namur in 1212 and left to her eldest son Philip when she went to Constantinople in 1216.

By Peter of Courtenay she had 10 children:

• Philip (d. 1226), Marquis of Namur, who declined the offer of the crown of the Latin Empire
• Robert of Courtenay (d. 1228), Latin Emperor
• Henry (d. 1229), Marquis of Namur
• Baldwin II of Constantinople (d. 1273)
• Margaret, Marquioness of Namur, who married first Raoul d'Issoudun and then Henry count of Vianden
• Elizabeth, who married Walter count of Bar and then Eudes sire of Montagu
• Yolanda, who married Andrew II of Hungary
• Eleanor, who married Philip of Montfort
• Marie, who married Theodore I Lascaris of the Empire of Nicaea
• Agnes, who married Geoffrey II de Villehardouin, Prince of Achaea