Margaret I (c. 1145 – died 15 November 1194) was the countess of Flanders suo jure from 1191 to her death.

Her claim was questioned by the king of France who, with support of Ghent, declared Flanders escheated to the crown due to the lack of male heirs, a problem that was not solved until the Treaty of Arras by the mediation of the archbishop of Reims.

[4] They met some unrest among the nobility of the area, foremost by her brother's widow, Theresa of Portugal, who was given extensive dower lands in the coastal and southern Flanders where she provoked considerable unrest by high taxation.

[4] The right of Margaret and her husband to the County of Flanders was not finally acknowledged until 1 March 1192.

[4] As countess, she objected to all foreign legal independence in her lands, and accordingly, she prevented the Hanse merchants living in Bruges from acquiring a separate quarter and rights for themselves in the port of Damme.