Bolshoy Begichev – an island among the Begichev Islands situated in the entrance to the Khatanga Gulf in the southwestern part of the Laptev Sea. It is part of the Sakha Republic (Yakutia). The area of the island is about 1,800 km2 with the total length of the shoreline amounting to 180 km. The length is 61 km and the width 57 km.
To the west there lies Maly Begichev Island (7 km wide) separated from B.B. by Pioneer Strait. 14 km to the north, there is Preobrazheniya Island. The distance from the southernmost point of B.B. Island to the mainland (the Nordvik Peninsula) is 9 km. The central part of the island belongs to a vast upland named Kiryaka with the highest point of 198 m. Almost radially from it, there lie several rivers, cutting through the Krutaya Gryada Range in the north (120 m high) and the short Meridiannaya Gryada Range (80 m high) in the east. The shores of the island are formed by loose marine and delluvial and soliflual depositions and are subject to abrasion, and on the eastern coast, there is a group of accumulative islands creating an island barrier. Long abrasive areas alternate with small accumulative forms. The northern shore is straightened and abrasive. Off the western shore of the island, there stretches westward the low Oleniy Peninsula 15 km long. The lowlands with many small lakes are abundant in the northwest, northeast, and southwest of the island, as well as in the Oleniy Peninsula.
The longest river is the Ilistaya (34 km). There are five rivers here with total length of more than 20 km. The island is marked by cryogenic processes and forms of relief caused by them: polygonal tundra, boolgunyakhs, and thermokarst. Significant areas of the coast are occupied by sandspits, and the northeastern end of the island is covered by friable sands (Keter-Kumak stow). The surface is covered with tundra vegetation. Polar foxes and reindeer live on the island and walruses in the coastal waters.
Until 1908, it was considered a peninsula after having been taken for it by mistake in 1736 by the head of Lena-Khatanga group of the Great Northern Expedition (1733–1743) V.V. Pronchishchev. Till the beginning of the twentieth century, cartographers repeated this mistake, though local traders at the time were aware of the existence of an island in this area. They called it Sizoy. B.B. was officially proven to be an island in 1908 by N.A. Begichev. He mapped its approximate position and named it Sizoy Island. It was more thoroughly studied by N.A. Begichev in 1910–1911. In 1912 the Russian Geographic Society gave it an official name in honor of its first researcher N.A. Begichev. Consequently after he discovered another small island in the Khatanga Bay, the former was named Bolshoy Begichev Island and the latter Maly Begichev Island.