Boyuk Alagol (Azerbaijani: Böyük Alagöl) is a lake in the Kalbajar District of Azerbaijan.

Its area is 5.1 square kilometres (2.0 sq mi) and the volume of water reaches 24,300,000 m3 (860,000,000 cu ft).

The surface of the lake is covered with ice up to one meter thick from early November to late April.

[3] The lake was occupied by Armenian forces following the First Nagorno-Karabakh war and was administrated as part of the Shahumyan Province of the self-proclaimed Republic of Artsakh.

The Kalbajar District, along with the lake, were returned to Azerbaijan on 25 November 2020 per the 2020 Nagorno-Karabakh ceasefire agreement.