This is a historic aqueduct in the city of Lisbon, Portugal. It is one of the most remarkable examples of 18th-century Portuguese engineering, including the largest stone arch in the world. The main course of the aqueduct covers 18 km, but the whole network of canals extends through nearly 58 km. The Mãe d'Água (Mother of the Water) reservoir of the Amoreiras, the largest of the water reservoirs, was finished in 1834. This reservoir, with a capacity of 5,500 m³ of water, was designed by Carlos Mardel. It is now deactivated and can be visited as part of the Museu da Água (Water Museum).

The Águas Livres Aqueduct (Portuguese: Aqueduto das Águas Livres; "Aqueduct of the Free Waters") is a historic aqueduct system in Lisbon, Portugal. It is considered one of the most remarkable examples of 18th-century Portuguese engineering and one of Lisbon's best-known landmarks.

The main aqueduct extends approximately 14.2 kilometres (8.8 mi), while the complete network of canals, galleries, reservoirs, and distribution systems reaches nearly 58 kilometres (36 mi). Its most famous feature is the monumental arcade crossing the Alcântara valley, including the Arco Grande, one of the tallest pointed masonry arches in the world.

Commissioned by King John V in the early 18th century, the aqueduct survived the 1755 Lisbon earthquake without significant damage.