Harcov Reservoir, Cultural monument lake in Kristiánov, Czech Republic.

Harcov Reservoir is a dam in the Harcov stream valley in Liberec-Kristiánov. Its curved granite masonry gravity dam, built to Otto Intze's design, is 20.5 m high and 157 m long, with a crest 13 m above the surrounding ground. The dam holds up to 630,000 m³ of water.

Built after the catastrophic flood of 30–31 July 1897, the dam was designed by Otto Intze, whose plans were approved in March 1901. Earthworks began in November 1902, the foundation stone was laid on 27 June 1903, and the reservoir was inaugurated on 29 April 1904. It was the first valley reservoir in Bohemia.

The reservoir takes its name from the Harcovský potok stream and the adjacent Starý Harcov district. In 1906 its banks hosted pavilions of the Deutschböhmische Ausstellung, and mock naval battles were staged on the water. A promenade was laid out along the right bank after completion.

The reservoir can be reached via Blahoslavova Street, which provides access to viewing areas and recreational spaces. Pathways and open areas allow visitors to explore the water and surrounding landscape.

The dam's profile follows Otto Intze's curved design, with a radius of 120 m and a crest just 4.5 m wide against a 16 m base. Stone for both faces came from three quarries inside the later flooded area, so the masonry was cut on the spot before the valley filled.