Esch-sur-Alzette is a city located in the southwestern region of Luxembourg, situated on the border with France. It lies within the valley of the Alzette river, which flows through the city. The city is approximately 15 kilometers (9.3 mi) south-east of the national capital, Luxembourg City.
As of 2025, Esch-sur-Alzette is the second-most populous commune in Luxembourg, with a population of 37,922 inhabitants. While it is frequently referred to simply as Esch, the full name is used to distinguish it from the village and commune of Esch-sur-Sûre, which is located 45 kilometers further north.