A megacity is usually defined as a recognized metropolitan area with a total population in excess of 10 million people.

Megacities around the world
Another list also defines megacities as urban agglomerations (continuous urbanization). Currently (2007), the agglomerations of more than 10,000,000 inhabitants are as follows :
(The above information is modeled for 2007 from population growth rates and is from [2] and [3]. The Manila figure is considerably higher than most lists, which limit their data to the administrative boundaries of Metro Manila. However, the continuous urbanization extends into Cavite, Laguna, Rizal and Bulacan provinces and is reflected in the higher figure in this list.)

Megacities defined as agglomerations
In Canada, the 1990s saw the forced amalgamation of several municipal entities in the provinces of Ontario and Quebec into a larger new municipalities. The process created what was labelled a megacity by the media.
Examples of megacities in Canada include:
For more information on Ontario "megacities," see the article on the Common Sense Revolution.

Toronto - the municipalities that constituted the Municipality of Metropolitan Toronto were merged into a new City of Toronto in 1998.
Kawartha Lakes, Ontario - the primarily rural Victoria County had its townships, towns and villages merged into a "megacity" in 2000. The area has a population of only 70,000 (several thousand less than nearby city Peterborough) yet takes up an area of 3,059.22 km² giving it a density of only a mere 22.6 persons per km².
Ottawa - the municipalities that constituted the Regional Municipality of Ottawa-Carleton were merged into a new City of Ottawa in 2001.
Gatineau - five municipalities in southwestern Quebec (Gatineau, Hull, Aylmer, Buckingham, and Masson-Angers) were merged into a new City of Gatineau in 2002.
Montreal - all of the municipalities on the island of Montreal were merged into a new City of Montreal for a short period of time until January 1st, 2006, when a partial demerger occurred. Naming scheme for megalopoleis