Seoul, South Korea... the capital of South Korea is the largest city in the world according to what I found. It has approximately 10.2 million people. Here is a site with the top 50, which is where I found this information: http://www.nationsonline.org/oneworld/bigcities.htm

Whilst Seoul has the largest population, Shanghai is believed to be the most densely populated city, having more population per square mile than any other.

Mexico City is the largest city in the world with a population of 16 million souls. See nationsonline.org. Not sure why this site does not list Mexico City anywhere in the top 50. But go to the Mexico City page on the site and check under "profile". I have seen some representations that put Mexico City at a population of 20 million. At any rate, it is head and shoulders above the second largest city. And it's just south of the USA border!

Shanghai, China with 13,278,500 in 2004.

Tokyo (with outskirts)

From nationsonline.org, there are basically two ways to determine city population: CITY PROPER, which counts only the city within the legal boundries. In other words, only people who are under the jurisdiction of that city government. OR URBAN AGGLOMERATION, which counts the city and the surrounding thickly settled, adjacent suburbs. For example: nationsonline.org lists my hometown, San Francisco, as having 776,733 people. (which seems about right) But if you include other parts of the Bay Area, the count for San Francisco comes to 7,039,362! So using the urban agglomeration method, there is no definite way to determine a city's population and whatever figure you come to will be up for debate because one can always argue which surrounding suburbs to include or exclude. Although... surrounding suburbs for many cities are really part of that city logistically. It's just a matter of how the local government drew the boundries. This is very apparent for some cities when looking at a population density map. Using the city proper method, Seoul Korea has the largest population with about 10 million people. (10 million people have Seoul, Korea as their mailing address)

According to National Geographc statistics, the most populous city in Africa is Lagos, Nigeria, with 16.9 million.

World's Most Populous Urban Agglomerations 1. Tokyo, Japan 35,327,000 2. Mexico City, Mexico 19,013,000 3. New York, U.S. 18,498,000 4. Mumbai (Bombay), India 18,336,000 5. São Paulo, Brazil 18,333,000 6. Delhi, India 15,334,000 7. Calcutta, India 14,299,000 8. Buenos Aires, Argentina 13,349,000 9. Jakarta, Indonesia 13,194,000 10. Shanghai, China 12,665,000

Seoul Korea as of Monday, Jul 30,2007 at 6:07:41pm

Tokyo.

Mumbai, India, with 13.6 Million, is number 1. Karachi, Pakistan is number 2, with 12.9 million. http://en.wikipedia.org/wiki/List_of_cities_by_population

According to http://en.wikipedia.org/wiki/List_of_cities_by_population , it's Mumbai, India with a population of 13,662,885.

According to wikipedia.org Mumbai, India with a population of 13,662,885 as of 1/1/2008