León (Spanish pronunciation: [leˈon]), officially León de Los Aldama, is the most populous city and municipal seat of the municipality of León in the Mexican state of Guanajuato. In the 2020 census, INEGI reported 1,579,803 people living in the city of León and 1,721,215 in the municipality, making it the fourth-most populous city and third-most populous municipality in Mexico. The metropolitan area of León recorded a population of 2,140,094 in the 2020 state census, making it the seventh most populous metropolitan area in Mexico. León is part of the macroregion of Bajío within the Central Mexican Plateau.
León has a large leather industry, making shoes, boots, belts, jackets, and other leather accessories for national and international markets. The leather industry earned its inhabitants the nickname of "green belly" (panzaverde in Spanish) because of the green tainting in the workers' bodies resulting from treating leather. Its first-class services and hotel industry make it an important commercial center in Mexico with numerous options for entertainment, gastronomy, leisure activities, arts, and recreation. It is also considered one of the most environmentally friendly cities in Mexico and has a high number of cyclists, in part because of integrating a network of bike lanes into the SIT system. In March 2012, it received an award as "City Water Champion", mainly due to great progress in the areas of sanitation, wastewater reuse, and energy cogeneration from biogas.