Belém Tower (in Portuguese Torre de Belém, [ˈtoʁ(ɨ) dɨ bɨˈlɐ̃ĩ]) or the Tower of St Vincent is a fortified tower located in the Belém district of Lisbon, Portugal, and is an UNESCO World Heritage Site (along with the nearby Jerónimos Monastery) due to the significant role it played in the Portuguese maritime discoveries of the era of the Age of Discoveries. The tower was commissioned by King John II to be both part of a defense system at the mouth of the Tagus River and a ceremonial gateway to Lisbon.

The tower was built in the early sixteenth century and is a prominent example of the Portuguese Manueline style, but it also incorporates hints of other architectural styles. The structure was built from lioz limestone and is composed of a bastion and the 30 meter (100 foot), four story tower. It has incorrectly been stated that the tower was built in the middle of the Tagus and now sits near the shore because the river was redirected after the 1755 Lisbon earthquake. In fact, the tower was built on a small island in the Tagus River near the Lisbon shore.

Lisbon (Portuguese: Lisboa; [liʒˈboɐ]) is the capital and largest city of Portugal. It is considered an alpha global city and is the seat of the district of Lisbon and the main city of the Lisbon region. Its municipality, which matches the city proper excluding the larger continuous conurbation, has a municipal population of 564,477 in 84.8 km² (33 sq mi), while the Lisbon Metropolitan Area in total has around 2.8 million inhabitants, and 3.34 million people live in the broader agglomeration of Lisbon Metropolitan Region (includes cities ranging from Leiria to Setúbal).

Due to its economic output, standard of living, and market size, the Grande Lisboa (Greater Lisbon) subregion is considered the second most important financial and economic centre in the Iberian Peninsula. The Lisbon region is the wealthiest region in Portugal and it is well above the European Union's GDP per capita average – it produces 37% of the Portuguese GDP. It is also the political centre of the country, as seat of government and residence of the Head of State.