Russian Lake is a large lake located in the northwest of Russia. It is made up of three interconnected lakes, Onega, Seg and Ilmen. Onega is the largest of the three and is located in the Republic of Karelia. Seg is the second largest and is located in the Leningrad Oblast region. Ilmen is the smallest of the three and is located in the Novgorod Oblast region. All three lakes are connected by the Volkhov River.