10,000 to 100,000. Iraq is one of the world's most populous country, ranking 37th with a population that exceeds 37 million. This country has many major cities that contribute heavily to this total population count. The largest city in the country is Baghdad, which has a population of over 5 million. Its next most populous city, Al Basrah, has a population of over 2.6 million -- a respectable number but still less than half of the population found in Baghdad. These aren't the only cities with populations exceeding 1,000,000.