Novosibirsk Reservoir or Novosibirskoye Reservoir (Russian: Новосиби́рское водохрани́лище), informally called the Ob Sea (Обско́е мо́ре), is the largest artificial lake in Novosibirsk Oblast and Altai Krai, Russian Federation.

It was created by a 33 m high concrete dam on the Ob River built in Novosibirsk.

The larger towns bordering the reservoir are Novosibirsk (Akademgorodok quarter, ObGES), Kamen-na-Obi and Berdsk.

Berdsk was severely impacted by the reservoir's construction, its historical centre having been submerged by the water.

[citation needed] During the summer, the lake is one of the most popular destinations for Novosibirsk residents, with many yachts and boats dotting the surface, and the beaches teeming with people.