Sergey Borisovich Ivanov (born 31 January 1953) is a Russian senior official and statesman. Ivanov was Minister of Defense of Russia from March 2001 to February 2007, Deputy Prime Minister from November 2005 to February 2007, and the First Deputy Prime Minister from February 2007 to May 2008. After the election of Dmitry Medvedev as President of Russia, Ivanov was reappointed a Deputy Prime Minister in Vladimir Putin's second government. From December 2011 to August 2016, Ivanov was the Chief of Staff of the Presidential Executive Office.

Ivanov's career, in terms of his background and rise through Russia's state structures, has often been compared to Putin's, fueling speculation that Ivanov might run for president. Three months younger than Putin, Ivanov had been a student contemporary of Putin's in their hometown of Leningrad where both completed competitive specialized secondary education programs (Putin in chemistry, Ivanov in the English language) before attending Leningrad State University. Both completed postgraduate studies in counterintelligence; and both joined the foreign intelligence service shortly afterward. However, according to Ivanov's recollections, he did not become acquainted with Putin during their years as students, but rather when both were assigned to work in the same foreign intelligence division in Leningrad.

On March 20, 2014, the Office of Foreign Assets Control (OFAC) announced that Ivanov and 19 others had been added to the Specially Designated Nationals List (SDN).