Portuguese Cistern is a historic cistern located beneath the Fortress of Mazagan in the city of El Jadida in Morocco. The cistern was originally built by the Portuguese during their construction of the castle in 1514 AD as a warehouse or armory, then it was converted into a water reservoir in 1541. The Portuguese Cistern was inscribed as a UNESCO World Heritage Site in 2004 as part of Portuguese City of Mazagan (El Jadida).