Judith (c. 844–870), also called Judith Martel, was a Frankish princess and wife to two kings of Wessex and the count of Flanders.

Judith was born probably in October of 844, the daughter of Charles the Bald, king of the Franks, and Ermentrude.

Her father gave her in marriage to Ethelwulf, King of Wessex on October 1, 856 at Verberie sur Oise, France.

Soon after this, Ethelwulf's son Ethelbald forced his father to abdicate. After his father's death on January 13, 858, Ethelbald married his widowed stepmother, but the marriage was annulled in 860 on the grounds of consanguinity.

She eloped with Baldwin I, Count of Flanders, in January 862. They were probably married at the monastery of Senlis before they eloped. They hid until October, when they went to her uncle Lothair for protection. From there they fled to Pope Nicholas I for protection. They were then officially married at Auxerre.

They had a son, Baldwin II, Count of Flanders, born in 864.

Judith died in 870.