Mikhail Mikhailovich Kasyanov (; born 8 December 1957) is a Russian politician who served as Prime Minister of Russia from 2000 to 2004. Previously he had served as First Deputy Prime Minister in 2000 and Minister of Finance from 1999 to 2000. During the 1990s he worked in President Boris Yeltsin's administration in different positions before joining President Vladimir Putin's first administration. Since leaving the government over disagreements on economic policy, he has become one of the leading critics of President Putin and an opposition leader.