Sidanko also transliterated as SIDANCO (Сиданко; Russian: Сибирско-Дальневосточная нефтяная компания, lit. 'Siberian-Far Eastern Oil Company') was a Russian oil company, the 8th largest company in the country by revenue in 1995.^[1] Sidanko owned several oil production units, including Chernogorneft and Udmurtneft.^[2]

Sidanko was established through the Decree No. 452 of the Russian government, published on 5 May 1994. The company counted among its assets oil extraction and processing facilities in the Udmurt Republic and in the Khanty-Mansiysk, Yamalo-Nenets, Irkutsk and Sakhalin regions.^[3] It was privatized in December 1995, when the Russian government auctioned off a 51% share as part of the loans for shares scheme.^{[4][lower-alpha 1]} The 51% stake was awarded to the bank Mezhdunarodnaya Finansovaya Kompaniya in return for a $130 million loan, guaranteed by Vladimir Potanin's Uneximbank.^[6] The company came under the ownership of Uneximbank, which exercised control over it through the Interros holding company.^[7]

An additional 34% stake was sold by the government in September 1996,^[8] in an auction designed to have Uneximbank as the only admissible bidder.^[9] As with the rest of the loan for shares scheme, the Sidanko auction was considered rigged by most analysts.^[10] In November 1997 British Petroleum bought a 10% share in the company for $484 million.^[2]

Sidanko entered bankruptcy proceedings in February 1999, after ZAO Beta Ekho filed to recover a $22,000 debt.^[11] Beta Ekho was later revealed to be a vehicle of Mikhail Fridman's Alfa Group, which was using bankruptcy laws to avenge Fridman's exclusion by Potanin from the Svyazinvest privatization.^[12] In September 1999 western creditors agreed to cede their voting rights in the company to Russian government.^[13]

Tyumen Oil Company bought Sidanko's Chernogorneft unit for $176 million at a bankruptcy auction in November 1999.^{[14][15][16][17]} In 2001 Interros sold a 44% stake in the company for $650 million.^[10] BP raised its stake to 25% in 2002, paying $375 million for a 15% share.^[18] In 2003 Sidanko merged with TNK, Onako and the majority of BP's oil assets in Russia to form TNK-BP.^[19]