The Sunny Lake (Polish: Jezioro Słoneczne), known until 1945 as the Reservoir (German: Stau See), is an artificial fresh water lake in Szczecin, Poland in the neighbourhood of Gumieńce, located near the intersection of Derdowskiego and Ku Słońcu Streets.

The artificial lake was formed in the 1930s, when a natural depression have been flooded by water, after surrounding it grounds have been developed into a house estate.

[1] In 2021, area surrounding the lake, commonly referred to as the Green Square Park, have been officially named the Adina Blady-Szwajger Park, after a physician and pediatrician active in the Warsaw Ghetto during the Second World War.

[2][3] It is a fresh water lark with an elongated shape, maximal length of 1.3 km, and maximal widght of 0.2 km, the total area of 2 ha, and the maximum depth of 2 m. It is crossed by the Bukowa river.

It induces the Love Island (Polish: Wyspa Miłości), connected to the mainland by a wooden bridge.