Yukio Hatoyama (yōō´kēō hätō´yämä), 1947–, Japanese politician, grad. Tokyo Univ. (B.S., 1969), Stanford (Ph.D, 1976). Though his grandfather was Prime Minister Ichiro Hatoyama and his father was foreign minister, he trained as an engineer and did not run for office until 1986, when he was first elected to the Diet. In 1993 he left the Liberal Democratic party (LDP), which his grandfather had cofounded, and served in a secondary cabinet post (1993–94) in a short-lived coalition government. Hatoyama cofounded the Democratic party of Japan (DPJ) in 1996, and later served as DPJ leader (1999–2002, 2009–10). In 2009, after the party's landslide win over the LDP, he became prime minister. He resigned as prime minister and DPJ leader in mid-2010 after he agreed, despite campaign promises to the contrary, to continue to permit the basing of U.S. forces on Okinawa. Naoto Kan succeeded him in both posts; Hatoyama retired from politics in 2012.