Réservoir des Lilas, Water reservoir in 19th arrondissement, France.

The Réservoir des Lilas consists of two parallel rectangular tanks, each 125 by 68 metres and 16 metres deep, set on either side of a 10-metre-wide alley. Built in 1963, it stores water from the Joinville-le-Pont treatment plant on the Marne and holds 208,000 m³, a little over a third of Paris's theoretical daily consumption. It lies within the square formed by boulevard Sérurier, the Robert-Debré hospital, the boulevard périphérique and allée Marius-Barroux.

The facility was built in 1963 as part of a major initiative to triple water storage capacity in eastern Paris districts. This expansion was necessary to meet the growing drinking water demand of the city during the post-war decades.

The reservoir takes its name from the nearby Porte des Lilas. Its two rectangular tanks, each 125 by 68 metres and 16 metres deep, sit on either side of a 10-metre-wide access alley. It is operated by Eau de Paris, the municipal water authority formerly known as SAGEP.

The reservoir is a working facility of Eau de Paris and is not open to visitors. It fills the block bounded by boulevard Sérurier to the south, the périphérique to the north, allée Marius-Barroux to the east and the Robert-Debré hospital to the west. From the surrounding streets you see only the grass-covered roof and its low concrete borders; the two tanks lie below ground.

The land where this facility stands belonged to the neighboring municipality of Pré-Saint-Gervais until 1930, when it was annexed to Paris. This boundary shift was part of the broader urban transformations that reshaped the eastern edge of the city during that era.