Hainaut (, also US: , UK: , French: [ɛno]; Dutch: Henegouwen [ˈɦeːnəɣʌuə(n)] (listen); Walloon: Hinnot; Picard: Hénau), historically also known as Heynowes in English, is a province of Wallonia and Belgium.

To its south lies the French department of Nord, while within Belgium it borders (clockwise from the North) on the Flemish provinces of West Flanders, East Flanders, Flemish Brabant and the Walloon provinces of Walloon Brabant and Namur.

Its capital is Mons (Dutch Bergen) and the most populous city is Charleroi, the province's urban, economic and cultural hub, the financial capital of Hainaut and the fifth largest city in the country by population. Hainaut has an area of 3,831 km² (1,479 sq mi) and as of January 2019 a population of 1,344,241. Another remarkable city is Tournai (Dutch Doornik) on the Scheldt river, one of the oldest cities of Belgium and the first capital of the Frankish Empire.

Hainaut province exists of a wavy landscape, except for the very southern part, the so-called Boot of Hainaut, which is quite hilly and belongs to the Ardennes and its foothills Fagne and the Condroz.

The village of L'Escaillère in the utmost southeastern corner is with an altitude of 365 metres the highest point of the province.

In the Boot of Hainaut on the border of Namur province the artificial five Eau d'Heure lakes are situated, the largest lake area of Belgium.

A well-known region is the Borinage, the old coal mining region around the city of Mons. Also well-known is the Pays des Collines (English Land of the Hills), a low hilly area forming one natural region with the Flemish Ardennes in the East Flanders province.