Like most cities, Lisbon has a rich history marked by wars, victories, defeats, golden eras and slumps. It's been ruled by the Romans and the Moors. It was in the last centuries of the Middle Age that the city expanded substantially and became an important trading post with both northern Europe and Mediterranean cities. Most of the Portuguese expeditions of the age of discovery left from Lisbon during the 15th to 17th centuries, including Vasco da Gama's departure to India in 1497. The 16th century marks the Golden Age for Lisbon. The city became the European hub of commerce with Africa, India, the Far East and later, Brazil, exploring riches like spices, slaves, sugar, textiles and other goods. Portugal lost its independence to Spain in 1580 after a succession crisis, and the 1640 revolt that restored the Portuguese independence took place in Lisbon.

Portugal derives its name from the Roman name, Portus Cale which means the Port of the Celts. The region was originally settled by pre-celts and celts and later conquered by Moors. In 1373, Portugal made an alliance with England, which is the longest-standing alliance in the world. At the end of the fourteenth century, Portugal spearheaded the exploration of the world and undertook the Age of Discovery. In 1415, Portugal gained the first of its overseas colonies when a fleet conquered Ceuta, a prosperous Islamic trade center in North Africa. This was followed by a series of colonizations including Madeira, Azores, Brazil, Goa in India and Malacca in Malaysia. Throughout the 15th century, Portuguese explorers sailed the coast of Africa, establishing trading posts for several common types of tradable commodities at the time, ranging from gold to slaves, as they looked for a route to India and its spices, which were coveted in Europe. In 1498, Vasco da Gama finally reached India and brought economic prosperity to Portugal and its then population of one million residents.

On 1 November 1755, Lisbon, the largest city and capital of the Portuguese Empire, was strongly shaken by an earthquake which killed thousands and destroyed a large portion of the city.  Portugal began a slow decline that was to follow until the 20th century. In 1910, a revolution deposed the Portuguese monarchy, but chaos continued and considerable economic problems were aggravated by the military intervention in World War I, which led to a military coup d'état in 1926. Portugal started losing its colonies in India and across Africa. Portugal's last overseas territory, Macau, was handed over to the People's Republic of China in 1999.

From the 1940s to the 1960s, Portugal was a founding member of NATO, OECD and EFTA. In 1986, Portugal joined the European Union (then the European Economic Community). In 1999, Portugal was one of the founding countries of the euro and the Eurozone. It is also a co-founder of the Community of Portuguese Language Countries (CPLP), established in 1996 and headquartered in Lisbon.