Gruža Lake, Reservoir in Šumadija District, Serbia.

Gruža Lake is an artificial reservoir on the Gruža River, impounded by a concrete arch dam built at Pajsijević in the municipality of Knić between 1979 and 1981; filling finished in 1983. It covers about 900 ha, is roughly 10 km long and 300 to 2,800 m wide, with an average depth of 6.5 m and a maximum of 35 m. The flooded valley created numerous capes and coves, and the bank is low and grassy, with steeper, partly rocky sections on the Knić side.

The project was planned in the 1970s and the lake began operations in 1983. It was built to provide a reliable water supply for the growing city of Kragujevac.

Since 1996 the slopes above the lake, in the hamlet of Žunja, host the annual "Gružanska jesen" art colony, drawing painters from Serbia and abroad. The lyric poet Dobrica Erić, called the "lyrical greeter of Gruža", promoted the lake in his verses. Fishing competitions are held often, thanks to the lake's size and its proximity to Knić and Kragujevac.

The lake lies southwest of Knić, with the dam and water treatment plant at Pajsijević. The northern part is 1,000–2,800 m wide, while the southern part narrows to 100–500 m near the dam. Banks are low and accessible, but the Knić side has rocky sections. In summer, low water shortens the shoreline by up to 3 km.

On 21 June 2018, four anglers needed three hours to land a wels catfish measuring 2.4 m and weighing 117 kg, caught in the shallow section known as the "Turkish wells". The lake also lies on the presumed Moravian-Vardar migration route, and 78 bird species have been recorded here, 25 of them nesting.