Lake Širvėna

Infobox lake
lake_name = Lake Širvėna
image_lake = Sirvenos_ezeras.jpg
caption_lake = Širvena lake as seen forn Northwestern corner of Biržai Castle
image_bathymetry =
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location = Biržai
coords = coord|56|12|43|N|24|45|18|E|type:waterbody_region:LT|display=inline,title
type = reservoir
inflow = Agluona, Apaščia
outflow =
catchment =
basin_countries = Lithuania
length =
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cities = Biržai, Astravas, Rinkuškiai

Širvėna Lake is a lake located in Biržai municipality, northern Lithuania. It is the oldest artificial lake in Lithuania. It was created in 1575 when the dam was built on rivers Agluona and Apaščia. The lake was built to protect the Radvila castle in Biržai. Now the city of Biržai, which was built around the castle, is located on the southern shore of Širvėna lake. The suburb of Astravas is built on the northern and the suburb of Rinkuškiai on the western shore.