Mahdia is a Tunisian coastal city with 76,513 inhabitants, south of Monastir and southeast of Sousse. Mahdia is a provincial centre north of Sfax…Mahdia is a Tunisian coastal city with 76,513 inhabitants, south of Monastir and southeast of Sousse. Mahdia is a provincial centre north of Sfax. It is important for the associated fish-processing industry, as well as weaving. It is the capital of Mahdia Governorate.