Luxembourg City is the capital city of the Grand Duchy of Luxembourg and the country's most populous commune. Standing at the confluence of the Alzette and Pétrusse rivers in southern Luxembourg, the city lies at the heart of Western Europe, situated 213 km (132 mi) by road from Brussels, 372 km (231 mi) from Paris, and 209 km (130 mi) from Cologne. The city contains Luxembourg Castle, established by the Franks in the Early Middle Ages, around which a settlement developed.

As of 31 December 2020, Luxembourg City has a population of 124,528 inhabitants, which is more than three times the population of the country's second most populous commune (Esch-sur-Alzette). The city's population consists of 160 nationalities. Foreigners represent 70% of the city's population, while Luxembourgers represent 30% of the population, and the number of foreign-born residents in the city rises steadily each year.

In 2011, Luxembourg was ranked as having the second-highest per capita GDP in the world at $80,119 (PPP), with the city having developed into a banking and administrative centre. In the 2011 Mercer worldwide survey of 221 cities, Luxembourg was placed first for personal safety, while it was ranked 19th for quality of living.

Luxembourg is one of the de facto capitals of the European Union (alongside Brussels, Frankfurt, and Strasbourg), as it is the seat of several institutions, agencies, and bodies of the European Union, including the Court of Justice of the European Union, the European Court of Auditors, the Secretariat of the European Parliament, the European Investment Bank, the European Investment Fund, the European Stability Mechanism, and Eurostat.

Places of interest include the Gothic Revival Cathedral of Notre Dame, the fortifications, Am Tunnel (an art gallery underground), the Grand Ducal Palace, the Gëlle Fra war memorial, the casemates, the Neumünster Abbey, the Place d'Armes, the Adolphe Bridge and the city hall. The city is home to the RTL Group.

The Second World War Luxembourg American Cemetery and Memorial is located within the city limits of Luxembourg at Hamm. This cemetery is the final resting place of 5,076 American military dead, including General George S. Patton. There is also a memorial to 371 Americans whose remains were never recovered or identified.