Barcelona is the capital and the most populous city of the Autonomous Community of Catalonia and the second largest city in Spain, after Madrid, with a population of 1,621,537 within its administrative limits on a land area of 101.4 km2 (39 sq mi). The urban area of Barcelona extends beyond the administrative city limits with a population of over 4,200,000 on a area of 803 km2 (310 sq mi), it is the sixth-most populous urban area in the European Union after Paris, London, Ruhr area, Madrid and Milan. About 5 million people live in the Barcelona metropolitan area. It is also Europe's largest metropolis on the Mediterranean coast. The main part of a union of adjacent cities and municipalities named Àrea Metropolitana de Barcelona (AMB) with a population of 3,186,461 in an area of 636 km² (density 5.010 hab/km²). It is located on the Mediterranean coast between the mouths of the rivers Llobregat and Besòs and is bounded to the west by the Serra de Collserola ridge (512 m/1,680 ft).

Barcelona is recognised as a Global City due to its importance in finance, commerce, media, entertainment, arts, international trade, education and tourism. Indeed, it is a major economic centre and a growing financial center (Diagonal Mar area); one of Europe's principal Mediterranean ports can be found here as well as Barcelona international airport, which handles about 30 million passengers per year. It also boasts an extensive motorway network and is a hub of high-speed rail, particularly that which will link France with Spain and later Portugal. Barcelona was the 12th-most-visited city in the world and 4th most visited in Europe after London, Paris and Rome. It is in addition the most popular tourist destination in Spain (receiving above 5 million tourists every year). Barcelona is the 15th most livable city in the World according to lifestyle magazine Monocle. Similarly, according to Innovation Analysts 2thinknow, Barcelona occupies 13th place in the world on Innovation Cities globally. It is the 6th richest city by GDP in Europe continent and 35th in the World amounting 177 billion euro and thus ?35,975 per capita (it is higher result of 44.4% from the average European Union's GDP per capita) and also, 29th place in terms of highest gross earnings in the World. The city is Europe's 3rd and one of the world's most successful city brands, both in terms of reputation and assets.

Founded as a Roman city, Barcelona became the capital of the Counts of Barcelona. After merging with the Kingdom of Aragon, it became one of the most important cities of the Crown of Aragon. Besieged several times during its history, Barcelona is today an important cultural centre and a major tourist destination and has a rich cultural heritage. Particularly renowned are architectural works of Antoni Gaudí and Lluís Domènech i Montaner that have been designated UNESCO World Heritage Sites. The city is well known in recent times for the 1992 Summer Olympics. The headquarters of the Union for the Mediterranean are located in Barcelona.