The Metropolis GZM is a metropolitan unit composed of 41 contiguous municipalities in the Silesian Voivodeship of Poland. The seat of the metropolitan council is Katowice, the largest city of the region and the voivodeship capital. With a population of over 2 million, the core of the Metropolis GZM is one of the largest urban areas in the European Union. The area of the metropolis largely coincides with the metropolitan area of the Katowice urban area, which is a part of the wider polycentric transnational Upper Silesian-Moravian metropolitan area, the latter with a population of 5–5.3 million people.

Katowice is the capital city of the Silesian Voivodeship in southern Poland and the central city of the Katowice urban area. As of 2021, Katowice has an official population of 286,960, and a resident population estimate of around 315,000. Katowice is a central part of the Metropolis GZM, with a population of 2.3 million, and a part of a larger Upper Silesian-Moravian metropolitan area that extends into the Czech Republic and has a population of around 5 million people, making it one of the most populous metropolitan areas in the European Union.