The 1991 Copa Libertadores was won by Colo-Colo of Chile after defeating Olimpia of Paraguay with a 3–0 aggregate score in the finals.

Twenty-one clubs from all South American countries within Confederación Sudamericana de Fútbol (CONMEBOL) participated.

Three clubs from Paraguay competed as Olimpia was champion of the 1990 Copa Libertadores.

First leg match played on May 29, 1991, in Asunción, Paraguay at Defensores del Chaco stadium.

Second leg final match played on June 5, 1991, in Santiago, Chile at Estadio Monumental David Arellano.