Lake Ladoga (Russian: Ла́дожское о́зеро, tr. Ladozhskoye ozero; IPA: [ˈladəʂskəjə ˈozʲɪrə] or Russian: Ла́дога, tr. Ladoga; IPA: [ˈladəgə]; Finnish: Laatokka [earlier in Finnish Nevajärvi]; Livvi-Karelian: Luadogu; Veps: Ladog, Ladoganjärv) is a freshwater lake located in the Republic of Karelia and Leningrad Oblast in northwestern Russia just outside the outskirts of Saint Petersburg.

It is the largest lake entirely in Europe, and the 14th largest freshwater lake by area in the world. Ladoga Lacus, a methane lake on Saturn's moon Titan, is named after the lake.