Konstantin Iosifovich Kosachev (Russian: Константин Иосифович Косачев; born 17 September 1962) is a Russian politician and former diplomat. He is a senator at the Federation Council (Russian parliament's upper house) and chairs its Foreign Affairs Committee. He has been on the US sanctions list since 2018.

After graduating from the Moscow State Institute of International Relations, Kosachev was a diplomat at the Russian Embassy in Sweden. He was elected to the State Duma in 1999. He was appointed head of Rossotrudnichestvo in 2012. In December 2014, he became a member of the Federation Council.

Konstantin Kosachev was born in the Pushkin district of Moscow Oblast on 17 September 1962 to Nina G. and Joseph Artemyevitch Kosachev, a diplomat who worked in the Ministry of Foreign Affairs of the USSR.^[1][2] He lived in Sweden eight years and attended school there. He later studied in Moscow, graduating in 1979.^[3]

In 1984, Kosachev graduated from the Moscow State Institute of International Relations. He is fluent in Swedish and English. As a translator, Kosachev worked in various diplomatic posts in the central and foreign offices of the Ministry of Foreign Affairs of the USSR and Russia. In 1991 he graduated from training at the Diplomatic Academy of the Ministry of Foreign Affairs.^[4]

Kosachev became First Secretary of Russian Embassy in Sweden in 1991. He was named advisor to the embassy in 1994. Kosachev participated in several international conferences on European security and disarmament. He was part of an advisory group to the Russia's Minister of Foreign Affairs. He was also deputy director of the 2nd European Department of the Russian Foreign Ministry, in charge of implementing Russian foreign policy in the Nordic area.^{[citation needed]}

From May 1998 Kosachev was first an adviser, then an assistant for international affairs to the Prime Minister (under Sergey Kiriyenko, Yevgeny Primakov, and Sergei Stepashin). He also served as Secretariat of the Chairman of the Government of the Russian Federation.^{[citation needed]}

In June 2010, Kosachev wrote an article for the Echo of Moscow website proposing that the Russian Federation devise set of principles or a historical doctrine whereby it could disclaim any financial, legal, political or moral responsibility for USSR's actions in former territories while still acting as a successor state.^[16][17]

In November 2011, he expressed the view that the European Monetary Union (euro zone) leave Greece, Hungary, Portugal, Ireland, Spain, Italy and Latvia, because these countries have a huge government debt.^{[18][clarification needed]} At that time, neither Latvia nor Hungary were part of the Eurozone.

Kosachev opposes Russian ratification of Article 20 of the United Nations Convention against Corruption. He believes that the 20th article contradicts Article 49 of the Constitution of the Russian Federation and could deprive millions of Russian citizens of the presumption of innocence.^{[citation needed]}

In February 2017, following the resignation of Michael T. Flynn as national security adviser, Kosachev opined that Russophobia was pandemic in Donald Trump's administration.^[19]

Kosachev spread the Ukraine bioweapons conspiracy theory, claiming without evidence that Ukrainians were being turned into genetically modified super soldiers in the alleged laboratories in Ukraine.^[20]

In September 2022, Kosachev warned that after the annexation referendums in Russian-occupied Ukraine, "protecting people in this region will not be our right, but our duty. An attack on people and territories will be an attack on Russia. With all the consequences."^[21]

• Order "For Merit to the Fatherland" 4th degree (20 April 2006) - for active participation in legislative work and many years of diligent work^[22]
• Order of Honour (7 December 2012) - for his great contribution to the preservation, promotion and development of Russian culture, education and the Russian language abroad^[23]
• Order of Friendship (21 January 2003) - for strengthening the rule of law, active legislative activity, and many years of diligent work^[24]
• Commander of the Order of the Polar Star (Sweden, 2004).^[25]
• Order of Friendship (South Ossetia, 17 October 2009) - for his great contribution to the maintenance of peace and stability in the Caucasus, strengthening of inter-parliamentary relations and active in championing the interests of the Republic of South Ossetia in the Parliamentary Assembly of the Council of Europe^[26]
• Medal of the Order "For Services to the Chuvash Republic" (10 March 2012) - for long-term work to defend the interests of the Chuvash Republic in the State Duma^[27]
• Honorary Doctor of Chuvash State University (28 March 2007)^[28]
• Honorary Doctor of the Institute of International Law and Economics. Griboyedov (2008)^[29]
• Samara Cross (Bulgarian Public Council)^[30]
• Order of Honour (South Ossetia, 14 April 2016)^[31]
• Envoy Extraordinary and Plenipotentiary Class 2 (29 September 1999)^[32]
• Ambassador Extraordinary and Plenipotentiary (1 December 2009)^[33]
• Acting State Advisor of the Russian Federation, Class 2 (25 January 1999)^[34]

Kosachev is a member of the Alexander Gorchakov Public Diplomacy Fund's Management Board.^[35]

Kosachev met his wife, Lyudmila Muranova (b. 1958) in Sweden.^[3] They have three children.^[4]