The Gulf of Finland (Estonian: Soome laht; Finnish: Suomenlahti; Russian: Фи́нский зали́в, romanized: Finskiy zaliv; Swedish: Finska viken) is the easternmost arm of the Baltic Sea.

It extends between Finland to the north and Estonia to the south, to Saint Petersburg - the second largest city of Russia - to the east, where the river Neva drains into it.

The depth of the Neva Bay is less than 6 metres (20 ft); therefore, in March 2019, a channel was dug at the bottom for safe navigation.

[4] The southern shores are smooth and shallow, but along the entire coast runs a limestone escarpment, the Baltic Klint, with a height up to 55 m (180 ft).

[9] The largest rivers flowing into the gulf are the Neva (from the east), the Narva (from the south), and the Kymi (from the north).

Keila, Pirita, Jägala, Kunda, Luga, Sista and Kovashi flow into the gulf from the south.

[11] As erosion progressed, the rivers encountered harder layers of Ordovician-aged limestone, leading to the formation of the cliffs of Baltic Klint in northern Estonia and Ingria.

[12][13] Later uplifting of the Baltic Shield skewed the surface of the gulf; for this reason, its ancient northern shores are significantly higher than the southern ones.

The major forest trees are pine, spruce, birch, willows, rowan, aspen, common and gray alder.

In the far eastern part of the gulf vegetation of the marshy areas consists mainly of bulrush and reeds, as well as fully aquatic plants, such as white and yellow waterlilies and acute sedge.

Humans began to inhabit these places soon after the ice age glaciers retreated and the water level of the Littorina Sea lowered to reveal the land.

They contain arrow tips and scrapers made of quartz, numerous food utensils and traces of fire camps – all indicative of hunting rather than agricultural or animal husbandry activities.

In 1559, during the Livonian War, the Bishop of Ösel-Wiek in Old Livonia sold his lands to King Frederick II of Denmark.

[20] As a result of the Russian defeat in the Ingrian War (1610–1617) and the Treaty of Stolbovo (1617) the lands on the Gulf of Finland and Neva River became part of the Swedish Ingria.

[19] Russia reclaimed the eastern part of the gulf as a result of the victory in the Great Northern War (1700–1721).

[22] The Russo-Swedish war ended in 1721 by the Treaty of Nystad, by which Russia received all the lands along the Neva and the Gulf of Finland, as well as Estland, Swedish Livonia and western part of the Karelian Isthmus, including Vyborg.

Estonia declared neutrality at the outbreak of World War II; however the country was repeatedly contested, invaded and occupied, first by the Soviet Union in 1940, then by Nazi Germany in 1941, and was ultimately reoccupied in 1944 by, and annexed into, the USSR as an administrative subunit (Estonian SSR).

Several ships still remain on the gulf bottom near Cape Juminda, and a monument was raised there in memory of those lost in the events.

[4][27] The southern coast of the gulf contains the Leningrad Nuclear Power Plant and a network of ports and unique natural and historical places.

Important goods include apatite from the Kola Peninsula, Karelian granite and greenstone, timber from Arkhangelsk Oblast and Vologda, ferrous metals from Cherepovets, coal from Donbas and the Kuznetsk Basin, pyrite from Ural, potassium chloride from Solikamsk, oil from Volga region, and grains from many regions of Russia.

[30] Passenger transport on the gulf includes a number of ferry lines which connect the following ports: Helsinki and Hanko (Finland), Mariehamn (Åland), Stockholm and Kapellskär (Sweden), Tallinn and Paldiski (Estonia), Rostock (Germany), Saint Petersburg and Kaliningrad (Russia), as well as many other cities.

[36] In September 2005 the agreement was signed on the construction of the Nord Stream 1 offshore gas pipeline on the Baltic Sea, from Vyborg to the German city of Greifswald.

A record was set in 1721 when during the evacuation of Russian troops from Finland, more than 100 vessels were lost within 3 months, including 64 in a single night.

[43] By the end of 1996, about 5,000 submerged objects were identified in the Russian part of the gulf, including 2,500 ships, 1,500 airplanes, and small items such as boats, anchors, tanks, tractors, cars, cannons, and even naval mines, aerial bombs, torpedoes, and other ammunition.

[44] These objects present potential hazards to navigation, fishery, coastal construction, laying of submarine pipelines and cables, and the environment.

There is significant contamination by ions of mercury and copper, organochlorine pesticides, phenols, petroleum products and polycyclic aromatic hydrocarbons.

Extraction of sand and gravel in the Neva Bay for the land reclamation destroy spawning sites of European smelt.

[49] Also worrying is expansion of oil ports in the gulf[49] and the construction of a treatment center for spent fuel from the Leningrad Nuclear Power Plant.

[50] The port of Kronstadt is currently serving as a transit point for the import in Russia of radioactive waste through the Baltic Sea.

The waste, mostly depleted uranium hexafluoride, is further transported through Saint Petersburg to Novouralsk, Angarsk and other cities of eastern Russia.