Luxembourg is one of the smallest countries in Europe, and ranked 179th in size of all the 194 independent countries of the world; the country is about 2,586 square kilometres (998 sq mi) in size, and measures 82 km (51 mi) long and 57 km (35 mi) wide. It lies between latitudes 49° and 51° N, and longitudes 5° and 7° E.

To the east, Luxembourg borders the German Bundesland of Rhineland-Palatinate and Saarland, and, to the south, it borders the French region of Lorraine. The Grand Duchy borders the Belgian Walloon Region, in particular the latter's provinces of Luxembourg and Liège, part of which comprises the German-speaking Community of Belgium, to the west and to the north respectively.

The northern third of the country is known as the 'Oesling', and forms part of the Ardennes. It is dominated by hills and low mountains, including the Kneiff near Wilwerdange, which is the highest point, at 560 metres (1,837 ft). Other mountains are the 'Buurgplaaz' at 559 metres near Huldange and the 'Napoléonsgaard' at 554 metres near Rambrouch. The region is sparsely populated, with only one town (Wiltz) with a population of more than four thousand people.

The southern two-thirds of the country is called the "Gutland", and is more densely populated than the Oesling. It is also more diverse, and can be divided into five geographic sub-regions. The Luxembourg plateau, in south-central Luxembourg, is a large, flat, sandstone formation, and the site of the city of Luxembourg. Little Switzerland, in the east of Luxembourg, has craggy terrain and thick forests. The Moselle valley is the lowest-lying region, running along the southeastern border. The Red Lands, in the far south and southwest, are Luxembourg's industrial heartland and home to many of Luxembourg's largest towns.

The border between Luxembourg and Germany is formed by three rivers: the Moselle, the Sauer, and the Our. Other major rivers are the Alzette, the Attert, the Clerve, and the Wiltz. The valleys of the mid-Sauer and Attert form the border between the Gutland and the Oesling.

According to the 2012 Environmental Performance Index, Luxembourg is one of the world's best performers in environmental protection, ranking 4th out of 132 assessed countries.

Confusingly, the capital city is also called Luxemburg.