Formerly South Korea's foreign minister, Ban Ki-Moon became the world's most important civil servant in 2007 when he took over the job of Secretary-General of the United Nations from Kofi Annan.

Ban is a career diplomat: He spent close to 40 years working at various posts around the world on behalf of South Korea. (He says he first dreamed of becoming a diplomat when he met President Kennedy at the White House as an 18-year-old student visiting Washington, DC.) He served as South Korea's minister of foreign affairs and national security advisor, where he headed up the country's negotiations with North Korea over that country's nuclear weapons program. When Secretary General Kofi Annan stepped down on December 31, 2006 after two five-year terms, the 15-member Security Council selected Ban to replace him. Low key and laid-back (or bland and uncharismatic, according to critics), Ban doesn't have the same sort of public profile that Annan had as Secretary General. But Ban's cool-headedness may just be what the U.N. needs these days. [Image via Getty]