The 1965–66 FIBA European Champions Cup was the ninth season of the European top-tier level professional basketball club competition FIBA European Champions Cup (now called EuroLeague). It was won by Simmenthal Milano, for the first time in its history, the first of the club's three EuroLeague championships.
Simmenthal defeated Slavia VŠ Praha, by a score of 77–72, in the final of the first ever Champions Cup Final Four held in the EuroLeague competition, with two venues used: a venue in Milan, and the Palazzo dello sport arena in Bologna, Italy. The Italian team, featuring future the Basketball Hall of Fame member Bill Bradley, defeated the favorites and former champs, CSKA Moscow, in the semifinal, by a score of 57–68.
26 teams. European national domestic league champions, plus the then current FIBA European Champions Cup title holders only, playing in a tournament system. The competition culminated in a Final Four.
*After a 130 aggregate drew, a third decisive game was held in which Wydad won 63–61.
* After a 148 aggregate drew, a third decisive game was held in which Zadar won 65–59.
Quarterfinals group stage
For the first time in the competition history, the quarterfinals were played with a round-robin system, in which every Two Game series (TGS) constituted as one game for the record.
Key to colors
||Top two places in each group advance to Semifinals
March 29, Milan
March 29, Palazzo dello sport, Bologna
3rd place game
April 1, Milan
April 1, Palazzo dello sport, Bologna