La Unión is a municipality in Colombia, located in the Eastern subregion of the department of Antioquia. It is bordered to the north by La Ceja and El Carmen de Viboral, to the east by El Carmen de Viboral, to the south by Abejorral, and to the west by La Ceja.
The municipality covers an area of 198 square kilometers. Its capital lies 57 kilometers from Medellín, the capital of the department of Antioquia.