The Fortress of Arad is a fortification system built in the city of Arad, on the left bank of the Mureş River in the 18th century at the direct order of the Habsburg Empress Maria Theresa. The fortress lies today in the Subcetate neighbourhood of the city, on the former military border between the Habsburg Empire and the Ottoman Empire. The fortress has been used during its existence as a military garrison, a military prison and today it is the home of the Mixed Romanian-Hungarian Battalion since 1999.
Following the victories of the Holy League at the Battle of Vienna and the Habsburg victory at the second Battle of Mohács the city of Arad has been freed from Ottoman rule. After the Treaty of Karlowitz, the entire city of Arad was on the border region of the Habsburg Empire and so, of critical importance for the Viennese Court as it became a focal point of the Military Frontier administration until 1751. The strategic placement of the city determined Prince Eugene of Savoy, to rebuild and improve the former rectangular Turkish built fortress, on the right bank of the river, but after consultations with the Empress, the decision was made not to rebuild the old fortress, but to erect a new and vastly improved fortified complex on the peninsula lying just south of the city.