Kuybyshev Reservoir or Kuybyshevskoye Reservoir (Russian: Ку́йбышевское водохрани́лище, Kuybyshevskoye Vodokhranilishche, Tatar Cyrillic: Куйбышев сусаклагычы, Latin: Kuybışev susaqlağıçı), sometimes called Samara Reservoir and informally called Kuybyshev Sea, is a reservoir of the middle Volga and lower Kama in the Chuvash Republic, Mari El Republic, Republic of Tatarstan, Samara Oblast and Ulyanovsk Oblast, Russia. The Kuybyshev Reservoir has a surface area of 6,450 km² and a volume of 58 billion cubic meters. It is the largest reservoir in Europe and third in the world by surface area.