The Great Northern Expedition (Russian: Великая Северная экспедиция) or Second Kamchatka expedition (Russian: Вторая Камчатская экспедиция) was one of the largest organised exploration enterprises in history, resulting in the mapping of most of the Arctic coast of Siberia and some parts of the North America coastline, greatly reducing the "white areas" on the maps. The endeavour was initially conceived by Russian Emperor Peter I the Great and implemented in practice by Russian Empresses Anna and Elizabeth. The main organiser and leader of the expedition was Vitus Bering, who earlier had been commissioned by Peter I to lead the first Kamchatka expedition. The Second Kamchatka expedition lasted roughly from 1733–1743 and later became called the Great Northern due to the immense scale of its achievements.
The goal of the expedition was to find and map the eastern reaches of Siberia, and to hopefully continue onto the western shores of North America to map them, as well. Emperor Peter I had a vision for the 18th-century Russian Navy to map the entire Northern Sea Route. This far-reaching endeavour was sponsored by the Admiralty College in St. Petersburg.
With over 3,000 people directly and indirectly involved, the Second Kamchatka expedition was one of the largest expedition projects in history. The total cost of the undertaking, completely financed by the Russian state, reached the estimated sum of 1.5 million rubles, an enormous amount for the period. This corresponded to one sixth of the income of the Russian state for year 1724.
The important achievements of the expedition included the European discovery of Alaska, the Aleutian Islands, the Commander Islands, Bering Island, as well as a detailed cartographic assessment of the northern and north-eastern coast of Russia and the Kuril Islands. The expedition also definitively refuted the legend of a land mass in the north Pacific. It also included ethnographic, historic, and scientific research into Siberia and Kamchatka. When the expedition failed to round the north-east tip of Asia, the dream of finding an economically viable Northeast passage, alive since the 16th century, was definitively at an end.