Fish Lake is a glacial lake in the Circus of the Seven Rila Lakes. They were formed by glaciation during the last glacial period about one million years ago. When the ice melted, they flowed into depressions formed in a circus among the slopes of the Rila mountain.

It is located at 2184 m above sea level and is the shallowest lake with a depth of 2.5 m and an area of 3.5 ha. The "Seven Lakes" lodge is located along the north-eastern shore of the lake. Ribno Lake is the shallowest of the Seven Rila Lakes.