The Llanos Basin (Spanish: Cuenca Llanos) or Eastern Llanos Basin (Spanish: Cuenca de los Llanos Orientales) is a major sedimentary basin of 96,000 square kilometres (37,000 sq mi) in northeastern Colombia. The onshore foreland on Mesozoic rift basin covers the departments of Arauca, Casanare and Meta and parts of eastern Boyacá and Cundinamarca, western Guainía, northern Guaviare and southeasternmost Norte de Santander. The northern boundary is formed by the border with Venezuela, where the basin grades into the Barinas-Apure Basin.