Arlon (French pronunciation: [aʁlɔ̃] ⓘ; Walloon: Årlon; Dutch: Aarlen [ˈaːrlə(n)] ⓘ; Luxembourgish: Arel [ˈaːʀəl] ⓘ) is a city and municipality of Wallonia, and the capital of the province of Luxembourg in the Ardennes, Belgium.

Other population centers include: Autelhaut, Clairefontaine, Fouches, Frassem, Freylange, Hachy, Heckbous, Rosenberg, Sampont, Schoppach, Sesselich, Seymerich, Stehnen, Sterpenich, Stockem, Udange, Viville, Waltzing, Weyler, and Wolberg.

The number and quality of sculpted stones and monuments that have been unearthed in the area demonstrate that the vicus of Orolaunum quickly became a commercial and administrative centre of Roman civilization.

The Germanic invasions of the 3rd century destroyed most of these early advances, despite the defensive walls that had been built on the Knipchen hill to protect the vicus.

In the 17th century, Capuchin friars built a convent on the ruins of the castle and the French strengthened the defensive walls according to Vauban's designs.

Arlon was one of the first victims of the German invasion in 1914 as 121 inhabitants were executed on 26 August, on the orders of Colonel Richard Karl von Tessmar.