The oblast overlaps the historic region of Ingria and is bordered by Finland in the northwest and Estonia in the west, as well as five federal subjects of Russia: the Republic of Karelia in the northeast, Vologda Oblast in the east, Novgorod Oblast in the south, Pskov Oblast in the southwest, and the federal city of Saint Petersburg in the west.
The oblast has an area of 84,500 square kilometers (32,600 sq mi) and a population of 1,716,868 (2010 Census); up from 1,669,205 recorded in the 2002 Census. The most populous town of the oblast is Gatchina, with 88,659 inhabitants (as of the 2002 Census). Leningrad Oblast is highly industrialized.
Leningrad Oblast is located around the Gulf of Finland and south of two great lakes of the European Part of Russia, Lake Ladoga and Lake Onega. Its northeastern part, between the Gulf of Finland and Lake Ladoga, occupies the Karelian Isthmus. Some islands in the Gulf of Finland (including Kotlin, on which the city of Kronstadt has been built) and Lake Ladoga (including Konevets) also belong to the oblast.
Much of the area of the oblast belongs to the drainage basin of the Neva, which is the only outflow of Lake Ladoga. Whereas the Neva, which flows to the Gulf of Finland (the city of Saint Petersburg is located in its river delta) is relatively short, its drainage basin is enormously big and includes Lake Onega and Lake Ilmen as well. The Svir and the Volkhov flow from Lake Onega and Lake Ilmen, respectively, to lake Ladoga. Other major tributaries of Lake Ladoga include the Vuoksi and the Syas. Rivers in the western part of the oblast flow to the Gulf of Finland; the two biggest rivers there are the Luga and the Narva, which makes the state border between Russia and Estonia. Minor areas in the east of the oblast belong to the river basin of the Chagodoshcha, a tributary of the Mologa, and of the Suda, both in the basin of the Volga. Thus, the divide between the basins of the Baltic and Caspian Seas crosses the oblast.
The Karelian Isthmus is a rocky terrain which hosts a lake district. The biggest lakes on the Karelian Isthmus are Lake Vuoksa, Lake Sukhodolskoye, and Lake Otradnoye. The rest of the area of the oblast is essentially flat. The exception is the Tikhvin Ridge, a chain of hills in the east of the oblast. Most of the area is covered by forests and swamps.
Leningrad Oblast contains two nature protected areas at the federal level, the Nizhnesvirsky Nature Reserve and Mshinskoye Boloto Zakaznik, both created to protect forest and swamp landscapes of northwestern Russia.