Lisbon (Portuguese: Lisboa; Portuguese pronunciation: [liʒˈboɐ]) is the capital and largest city of Portugal, with a population of 479,884 within its administrative limits on a land area of 84.8 km2 (33 sq mi). The urban area of Lisbon extends beyond the administrative city limits with a population of 2.4 million on a area of 958 km2 (370 sq mi), it is the 12th most populous urban area in the European Union. About 2,831,000 people live in the Lisbon Metropolitan Area (which represents approximately 27% of the population of the country) and 3.34 million people live in the broader agglomeration of Lisbon Metropolitan Region (includes cities ranging from Leiria to Setúbal). Lisbon is the westernmost large city located in Europe, as well as its westernmost capital city. It lies in the western Iberian Peninsula on the Atlantic Ocean and the Tagus River, about 320 km (198.84 mi) northwest of Cape Spartel in Africa.

Lisbon is recognised as an Alpha World City because of its importance in finance, commerce, media, entertainment, arts, international trade, education and tourism. It is one of the major economic centres on the continent, with a growing financial centre and the largest/second largest container port in the "Europe's Atlantic coast", Lisbon International Airport serves about 13 million passengers per year, motorway network and hub of high-speed rail (Alfa Pendular) linking main cities in Portugal, and in 2013 will have a rail's high-speed connection to Spain. Lisbon is the 25th most livable city in the World according to lifestyle magazine Monocle. The city is the 6th-most-visited city in Southern Europe after Rome, Barcelona, Madrid, Athens and Milan with about 2 million tourists a year. The Lisbon region is the wealthiest region in Portugal, GDP PPP per capita is 26,100 euros (it is higher results of 4.7% from the average European Union's GDP PPP per capita). It is the 10th richest metropolitan area by GDP on the continent amounting to 98 billion euros and thus €34,850 per capita, it is higher result of 40% from the average European Union's GDP per capita. The city occupies 32nd place of highest gross earnings in the world. Most of the headquarters of multinationals in the country are located in the Lisbon area and it is the 9th city in the world in terms of quantity of international conferences. It is also the political centre of the country, as seat of government and residence of the Head of State. The seat of the district of Lisbon and the centre of the Lisbon region.

Lisbon enjoys a Subtropical-Mediterranean climate, and through strongly influenced by the Gulf Stream it is one of the mildest climates in Eurasia. Among all the metropolises in Europe, here are the warmest winters on the continent, with average temperatures above 15.2 °C (59.4 °F) during the day and 8.9 °C (48.0 °F) at night in the period from December to February. The typical summer's season lasts about 6 months, from May to October, with an average temperature of 25 °C (77 °F) during the day and 16.2 °C (61.2 °F) at night, although also in November, March and April sometimes there are temperature above 20 °C (68.0 °F) with an average temperature of 18.5 °C (65 °F) during the day and 11.2 °C (52.2 °F) at night.

Lisbon is one of the oldest cities in the world. Julius Caesar made it a municipium called Felicitas Julia, adding to the name Olissipo. Ruled by a series of Germanic tribes from the 5th century, it was captured by Moors in the 8th century. In 1147, the Crusaders under Afonso Henriques reconquered the city for the Christians and since then it has been a major political, economic and cultural centre of Portugal. Unlike most capital cities, Lisbon's status as the capital of Portugal has never been granted or confirmed officially – by statute or in written form. Its position as the capital has formed through constitutional convention, making its position as de facto capital a part of the Constitution of Portugal.

Lisbon hosts two agencies of the European Union, namely, the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) and the European Maritime Safety Agency (EMSA). The Community of Portuguese Language Countries (CPLP), is also headquartered in Lisbon.

Lisbon has two sites listed by UNESCO as a World Heritage Site: Belém Tower and Jerónimos Monastery. Furthermore, in 1994, Lisbon was the European Capital of Culture and in 1998 organized an Expo '98 (1998 Lisbon World Exposition).

The city is candidate for the 2020 Summer Olympics.