Barragem Atibainha, Water management dam in Nazaré Paulista, Brazil

Barragem Atibainha is a dam on the Atibainha River in Nazaré Paulista, São Paulo state, forming the Represa Atibainha reservoir. The dam stands 29 metres high, and the reservoir covers 1,557.65 hectares with a capacity of 290.78 million cubic metres. It belongs to SABESP and is part of the Cantareira System.

The dam was built in 1975 as part of the Cantareira System to supply water to the São Paulo metropolitan region. It connects multiple reservoirs through tunnels and serves as a key part of the regional water network.

The reservoir's name comes from the Atibainha river, a tributary of the Atibaia. Since March 2018 the Jaguari–Atibainha link has carried about 5,100 litres per second from the Paraíba do Sul basin into the Cantareira System, a transfer visitors hear about as the region's answer to the 2014–2016 water crisis.

The dam area is accessible during daylight hours with several spots where you can view the water structure. Good footwear is recommended since some areas near the dam can be uneven or slippery.

The structure is part of a complex system of tunnels that transport water between different reservoirs to optimize distribution across the region. These underground connections allow water to be moved based on changing needs.