Jeanne of Ponthieu

Jeanne de Ponthieu, dame d'Épernon, Countess of Vendôme and of Castres (Jeanne de Ponthieu, dame d'Épernon, comtesse de Vendôme et de Castres, before 1336 – 30 May 1376) was a French noblewoman, the youngest daughter of Jean II de Ponthieu, Count of Aumale. She was the wife of Jean VI de Vendôme, Count of Vendôme and of Castres. She acted as regent for her infant granddaughter Jeanne, suo jure Countess of Vendôme from 1371 until the child's premature death in 1372.

Jeanne was born in France sometime before 1336, the youngest daughter of Jean II de Ponthieu, Count of Aumale, and Catherine d'Artois (1296 – November 1368). She had an elder sister Blanche de Ponthieu (before 1326 – 12 April/May 1387) who became suo jure Countess of Aumale on 16 January 1340 upon the death of their father. Blanche was the wife of Jean V de Harcourt, Count of Harcourt, by whom she had issue.

Jeanne, who was also known as the Dame d'Épernon, was a direct descendant of King Ferdinand III of Castile by his second wife Joan, Countess of Ponthieu. King Louis VIII of France and Blanche of Castile were also among her many royal ancestors. Her paternal grandparents were Jean I de Ponthieu, Count of Aumale and Ide de Meullent. Her maternal grandparents were Philip of Artois and Blanche of Brittany, also known as Blanche de Bretagne, herself the granddaughter of King Henry III of England and Eleanor of Provence. The seigneury of Épernon was part of her father's inheritance which came into his family about 1256 upon the marriage of his grandmother Laure de Montfort, Dame d'Épernon to the Infante Ferdinand of Castile, Count of Aumale.