The 1965–66 Yugoslav First League season was the 20th season of the First Federal League (), the top level association football league of SFR Yugoslavia, since its establishment in 1946. Sixteen teams contested the competition, with Vojvodina winning their first national title. Revelation of match-fixing from May–June 1964 ("Planinić affair") Though the events in question had taken place fourteen months earlier, the beginning of the 1965-66 season and subsequently the rest of the campaign were marked by revelations of match fixing from May and June 1964, during the concluding weeks of the 1963-64 season. In late August 1965, two weeks into the new league season, FK Željezničar, Hajduk Split, and NK Trešnjevka were found guilty of fixing matches from two seasons earlier at the end of the 1963-64 season. Their guilt was based on a written statement by the Željo goalkeeper Ranko Planinić who decided to come forward some 14 months after the fact. In his statement, Planinić claims on the record that his club threw matches against Hajduk and Trešnjevka towards the end of the 1963-64 season in return for financial compensation that those two relegation-threatened teams paid in order to avoid the drop. Specifically, Planinić claims that the match played on 31 May 1964 in Split when Hajduk beat Željezničar 4-0 was fixed, as well as the match on 7 June 1964 in Sarajevo when Željo and Trešnjevka tied 3-3. He was in Željo's goal for both matches. Planinić made the information public in August 1965 by approaching the Večernje novine journalist Alija Resulović who in turn took Planinić's testimony in form of an interview and the piece was published by the paper, circulated in 100,000 copies at the time. In his 2006 book Ona vremena, Resulović claims to have contacted FK Željezničar's president Nusret Mahić right before submitting the piece for print, informing him of Planinić's allegations, seeking comment, and even offering to sit on the information if he (Mahić) thinks it necessary. Resulović further claims that Mahić's response was: "Publish it all! It's all a lie that Planinić concocted as revenge for being fined for an incident he caused at a training session". The explosive testimony immediately erupted in a nationwide scandal that became known as the 'Planinić Affair'. Yugoslav First League had been plagued by rumours of widespread match-fixing on multiple occasions over the preceding decade, however, this was the first occasion that a player