Situated in the southeast section of the medina, the Mosque Sidi of Youssef Ben Ali is the largest mosque in the city of Essaouira. According to the site of the Moroccan Ministry of Habous it was constructed between 1773-1774/1187 AH by Abu Yaqub Yusuf Ibn Muhammad Ibn Sidi Mohammed Ibn Annacer al-Tamagrouti, one of the Imams who had accompanied the Sultan Sidi Mohammed Ibn Abdellah at the founding of the city of Essaouira. It is an important and imposing building, with a facade on the Méchaour.
Occupying an area is approximately 2080 m², it is a typical Moroccan mosque. The prayer hall is composed of three naves running parallel to the qibla wall. The courtyard measures 35mx13m.