It was possibly the biggest upset in any European club final to date.
In a match where it seemed FC Internazionale Milano were destined to claim the trophy for the third time, Steve Chalmers' winner six minutes from the end ensured it was Celtic FC and their 15,000-strong following that celebrated in Lisbon.
Never before had the European Champions Clubs' Cup been won by a side outside the southern powerhouse cities of Madrid, Lisbon and Milan. And while the great Real Madrid CF, SL Benfica, Inter and AC Milan teams of the past had boasted talents from South America and Africa, all of Celtic's players were from the locality of Glasgow.
Seven minutes in, however, Inter seemed to be on course. Jim Craig fouled Renato Cappellini in the box, and Alessandro Mazzola put away the penalty.
Admittedly, seven of the eleven previous European Cup finals had been won by the side conceding the first goal, but as Benfica discovered two years previously in Milan, Helenio Herrera's catenaccio defence of Tarcisio Burgnich, Giacinto Facchetti, Aristide Guarneri and Gianfranco Bedin took some beating.
Inter had actually been expansive before the goal, Mazzola forcing a save from Ronnie Simpson, but now the door was locked. That said, Celtic were still able to test Giuliano Sarti in their opponents' goal, Berti Auld striking the crossbar and the goalkeeper denying Jimmy Johnstone on two occasions.
The hour mark arrived, and still Inter held a familiar 1-0 lead. Yet three minutes later that advantage disappeared, Tommy Gemmill, who had already had a speculative effort hit the crossbar, beat Sarti with a vicious shot.
Now everything was different, as the towering Facchetti later admitted: "We were shocked, this was not supposed to be happening."
Perhaps it was the eight scouting trips Celtic had made to examine Inter. Or maybe it was a conversation about the secrets of catenaccio and Herrera's system that the Scottish side's manager Jock Stein had with Facchetti in December 1965.
Either way, Celtic now held the initiative, and began pushing for a winner while Inter struggled to leave their self-imposed defensive rut and were eventually made to pay.
Six minutes from time, Bobby Murdoch's shot from the edge of the area was deflected past Sarti by Chalmers. In an incredible season for the Scottish champions, it was their 200th goal ... and the most important.