Medellín (Spanish pronunciation: [meðeˈʝin]), officially the Municipio de Medellín (Spanish) or Municipality of Medellín, is the second largest city in Colombia. It is in the Aburrá Valley, one of the more northerly of the Andes in South America. To 2012, it has a population of 2.7 million. With its surrounding area, the metropolitan area of Medellín (área metropolitana de Medellín), composed by another nine cities, it is the second largest urban agglomeration in Colombia in terms of population and economy, with more than 3.5 million people.

Medellín was founded in 1616 by the Spaniard Francisco Herrera Campuzano as Poblado de San Lorenzo (Saint Lawrence Town) in present-day El Poblado. In 1675 the queen consort Mariana of Austria created the Villa de Nuestra Señora de la Candelaria de Medellín (Town of Our Lady of Medellín).

In 1826 the city was named the capital of the Department of Antioquia by the National Congress of the young Republic of Greater Colombia (Gran Colombia), comprised by present day Colombia, Venezuela, Ecuador and Panama. In 1803 the University of Antioquia, one of the most prestigious in Colombia, was founded. After Colombia won its independence from Spain, Medellín became the capital of the Federal State of Antioquia until 1888, with the proclamation of the Colombian Constitution of 1886. During the 19th century, Medellín was a dynamic commercial center, first exporting gold, then producing and exporting coffee. After the Thousand Days War (1899 — 1902), Medellín was the first Colombian city to take part in the Industrial Revolution with the opening of textile companies, and transport projects such as railways that allowed its export business to develop. In addition, its people founded several universities and vocational training institutions.