If you are talking about a continuous civilization with the same ruling class, then the oldest civilization would have to be The People's Republic of China. Although they are now the inheritors of the old line communists, the basic type of government (dictatorial and hereditary) has been in China the longest. Some people may assume it's Iran, but there have been many periods in the history of Iran where due to war or natural disaster that Iran has been 'off the map' or has been run by people from other countries entirely, therefore their civilization doesn't count and more than Egypt's or any other of the countries in what we now call the Middle East and Africa.
