San Agustín Lanquín, often referred to simply as Lanquín, is a municipality in the Guatemalan department of Alta Verapaz. It lies at an altitude of 380 m above sea level. It has a population of about 16,500 people, many of Q'eqchi' Maya descent. It covers an area of 208 km².

Alta Verapaz is a department in the north central part of Guatemala. The capital and chief city of the department is Cobán. Verapaz is bordered to the north by El Petén, to the east by Izabal, to the south by Zacapa, El Progreso, and Baja Verapaz, and to the west by El Quiché.