Mostaganem (Arabic: ولاية مستغانم) is a province (wilaya) of Algeria. Its capital is Mostaganem.

The land relief in Mostaganem Province can be divided into four regions: the Dahra Range to the east, the Mostaganem Plateau to the south, the Chelif River valley which separates the two highland regions, and the plains on the province's southern border which lie next to the marshes of the Macta.

The Mostaganem Plateau covers eleven municipalities in the southern part of the province: Mostaganem, Ain Tedles, Sour, Bouguirat, Sirat, Souaflia, Mesra, Ain Sidi Cherif, Mansourah, Touahria and Sayada. It is a semi-arid and sandy plateau, in the shape of a triangle and bounded to the north by the Chelif River. It receives 350 mm of rainfall per year.

During French colonization, viticulture was introduced on the plateau. After the country's independence, it was replaced by irrigated market gardening and the culture of citrus fruits and cereals. However, in certain sectors east of Mostaganem, the replacement of the vineyards caused the appearance of small dunes as a consequence of the resumption of soil movement.

In 1984 Relizane Province was carved out of its territory.

The province is divided into 10 districts (daïras), which are further divided into 32 communes or municipalities.