Saudi Aramco ranks number One on Forbes magazine's list of The World's 25 Biggest Oil Companies. The list, which was released Tuesday, saw Saudi Aramco at the top, Russia's Gazprom came in second and National Iranian Oil took third position. These oil companies were followed by ConocoPhillips, Exxon Mobil, British Petroleum (BP), Royal Dutch Shell and Chevron in the same order. Forbes magazine is a leading source for reliable business news and financial information.