Mariembourg (French pronunciation: [maʁjɑ̃buʁ]; Walloon: Mariyambour) is a town in the municipality of Couvin in the Province of Namur, Belgium.

At Mary's initiative, the fortress of Mariembourg was created in 1542–1546 on land which had earlier belonged to the Floreffe Abbey.

[1] The fortress town, which at its completion was considered impenetrable, was besieged by French troops in 1554 and taken only three days later.

[2] The central square, formally called Place Marie de Hongrie but also referred simply to as Grand Place, is the location of the church, built in 1542 in a Renaissance style, and the former town hall from 1884, built in a Gothic revival style.

[1][3] The town is served by the heritage railway Chemin de fer à vapeur des Trois Vallées, as well as by regular train services.