Oeiras is a municipality in the western part of Lisbon metropolitan area, a subregion of Greater Lisbon, in continental Portugal. It is part of the urban agglomeration of Lisbon, 16 km from the capital. The municipality is the fifth-most densely populated in Portugal.

Oeiras is an important economic hub, being one of the most highly developed municipalities of Portugal and Europe. It has the highest GDP per capita in the country, being also the second highest municipality (immediately after Lisbon) in terms of purchasing power as well as the second one collecting taxes in the country. These economic indicators also reflect the education level of the inhabitants, as Oeiras is the municipality with the highest concentration of population with higher education in the country. It also has the lowest unemployment rate in the Lisbon area.

Oeiras offers a range of points of interest, ranging from monuments of unique and historical value, such as the Palace of Marquês de Pombal and Palace of the Royal Estate in Caxias (that dates from the 18th century and surrounded by luxurious gardens) to sites with industrial history, like the Fábrica da Pólvora de Barcarena ('Barcarena Gunpowder Factory'), a reclaimed arms factory used for leisure and cultural purposes.

Leisure facilities include the sports complex of Jamor, Oeiras' promenade (linking Algés and Oeiras e São Julião da Barra) and the yacht harbour, in addition to other local parks and green spaces. The modern Parque dos Poetas ('Poets' Park'), a green space with statues of Portuguese poets and writers, is also one of the ex-libris of Oeiras. Many of the former town centres have been recovered, displaying monuments and tourist-oriented venues for leisure, cultural, gastronomic and social events (for example the town of Paço de Arcos).