Russia's acting Prime Minister since May 2000. Born 1957.
Mikhail Kasyanov is a liberal economist and a technocrat with a good reputation among Western investors. He is well-known in the West from his work over several years as Russia's chief debt negotiator. He is Mr Putin's junior by five years, and a fluent English-speaker.
Mr Kasyanov graduated from Moscow's Automobile and Road Institute, and later worked at Gosplan, the Soviet Union's all-powerful economic planning agency. He worked in Russia's Economics Ministry from 1990 to 1993, when he joined the Finance Ministry, later becoming Russia's "Mr Debt".
He moved rapidly up the ministry's ranks, becoming deputy Minister, then first deputy minister, and finally minister of finance in May 1999. He held on to this post when he was appointed first deputy prime minister in January 2000.
As first deputy prime minister, he has been in charge of day-to-day running of the government and President Vladimir Putin kept him in that role - primarily as a manager rather than a policy-maker.
Mr Kasyanov has spent 10 years in the economics and finance ministries, and his appointment as acting Prime Minister consolidated a shift in Russia towards a younger generation of political leaders.
At the moment of his appointment, most observers saw Mr Kasyanov as a figure independent of Russia's financial clans who would help Mr Putin eradicate the political influence of the country's super-rich tycoons, or "oligarchs". A minority of analysts have, nonetheless, suggested that Mr Kasyanov was close to Boris Berezovsky, who exercised a major influence over President Boris Yeltsin's inner circle.
Nevertheless, in October 2003, when Yukos oil company ex-CEO Mikhail Khodorkovsky was arrested, Kasyanov was blamed by a number of Russian lawmakers for giving free rein to the oligarchs. Vladimir Yudin, the deputy head of the Duma's economic policy and entrepreneurship committee, said Kasyanov had turned a blind eye to tax evasion by big business and that he "had to be held responsible for this." He also hinted that he may at one point produce evidence that Kasyanov, who criticized prosecutors for their handling of the Yukos case despite warnings from the Kremlin not to do so, was himself embroiled in corruption.
At the same time, Mr Kasyanov has lost a powerful Kremlin ally in Alexander Voloshin, and has become the main target for attacks.
So now it is clear that if the president does not protect him, he will just be swept away.