Rudolph William Louis Giuliani (/ˈruːdi ˌdʒuːliˈɑːni/; born May 28, 1944) is an American lawyer, businessman, public speaker, former mayor of New York City, and an informal adviser on cybersecurity to the White House.
Politically a Democrat, then an Independent in the 1970s, and a Republican since the 1980s, Giuliani was the United States Attorney for the Southern District of New York during the 1980s. Giuliani prosecuted pivotal cases against the American Mafia, and against corrupt corporate financiers.