Vartry Reservoir (Irish: Taiscumar Fheartraí) is a reservoir on the Roundwood plateau in north Wicklow. The water is piped from Vartry River to a large open service reservoir in Stillorgan in the southern suburbs of Dublin. The reservoir is operated by Dublin City Council.
The original (lower) reservoir was completed in 1863 and has a capacity of 11.3 billion litres and a maximum depth of 18.3 metres. A second embankment, 3.5 km upstream, was completed in 1923 to form the upper reservoir. This has a capacity of 5.6 billion litres and a maximum depth of 13.4 metres.
The creation of the reservoir was particularly important in improving living conditions and public health in Dublin city. Access to clean water improved sanitation and helped reduce outbreaks of cholera, typhus and other diseases associated with contaminated water.