The European Cup of National Champions 1965/66 was the 11th edition of the competition. 31 club teams took part, including 30 national champions from the previous season and the defending champions with Inter Milan .
The participants played in a pure cup mode with (except for the finals) back and forth games for the crown of European club football. In the case of a tie, the higher number of goals scored away counted in the first two rounds and a play-off was due from the quarter-finals. If there was still no decision, a coin was tossed.
The final took place on May 11, 1966 in the Heysel Stadium in Brussels in front of a good 55,000 spectators.