Yukio Hatoyama (鳩山由紀夫, Hatoyama Yukio?, born 11 February 1947) is a Japanese politician who has been Prime Minister of Japan since September 2009. First elected to the House of Representatives in 1986, Hatoyama became President of the Democratic Party of Japan (DPJ), the main opposition party, in May 2009. He then led the party to victory in the August 2009 general election, defeating the long-governing Liberal Democratic Party (LDP). He represents the 9th district of Hokkaidō in the House of Representatives.

Hatoyama is only the second Japanese Prime Minister to be born after the end of World War II; the first was Shinzō Abe.

Hatoyama comes from a prominent Japanese political family which has been called the "Kennedy family of Japan."