The showpiece event was contested Competition between defending Defending champions Peñarol and Santos .

Two-time winners Peñarol were appearing Presence in their third consecutive final , whereas Santos were seeking to win Getting the competition for the first time .

Ten teams entered Arriving the competition in its third season and , due to the rules in place at the time , Peñarol received Receiving a bye into the semifinals and reached Arriving the final having won only one match in the semifinal round .

In the semi-finals , Peñarol drew 2-2 on points with classic rivals Nacional after they each won a match .

A playoff was contested Competition in order to break Process_end the tie ; the match ended Process_end in a draw and Peñarol went through due to their better total goal difference .

Santos would go on to dethrone Peñarol after winning Getting the playoff 3-0 to win Getting the coveted throphy and become Becoming the second champions of this prestigious event .

The finals were contested Quarreling in two-legged home-and-away format between Uruguayan team Peñarol and Argentine team Club Atlético River Plate .

The first leg was hosted Social_event by Peñarol at Estadio Centenario in Montevideo on 12 May 1966 , while the second leg was hosted Social_event by River Plate at Estadio Monumental in Buenos Aires on 18 May 1966 .

Peñarol beat Competition River by 4–2 therefore winning Getting their 3rd .

Both finalists reached Arriving the final with relative ease as they crushed Botafogo and Peñarol .