1947–1976 NK Osijek was founded on 27 February 1945 as NK Udarnik on the tradition of banned
JŠK Slavija Osijek, which was founded in 1916 and played in the first Yugoslavia League seven times between 1923 and 1941. In 1946, the club had been merged with Jedinstvo and changed its name to
NK Slavonija. The conventional anniversary of the club is considered to be the following year on 27 February 1947, when NK Slavonija and NK Bratstvo merged to form
FK Proleter. The first match played under that name comes the 16th of March of that same year, when Proleter beat city rivals Mladost by five goals to nil. The first competition in which the club participated in was the Osječko Okružno Prvenstvo, along with four other teams. The club got into the second national league soon after. Proleter achieved placement into the
Yugoslav First League in 1953, having won the so-called Croato-Slovenian League. The best players from that side were Andrija Vekić,
Franjo Rupnik,
Dionizije Dvornić and Franjo Majer. Proleter played in the First League for three seasons, but were then relegated to the second division. Proleter moved to current
Gradski vrt stadium in autumn 1958 and changed its name to
Slavonija as part of the unifying process of the boxing, athletics and Olympic lifting club in a newly founded sports association in 1962. It still plays in the second league. Five years later the association is disbanded and the club took on the name
NK Osijek. The then-colours red and blue were switched to current colours blue and white. In 1970, Osijek won the 2nd North League Championship. However,
Borac Banja Luka beat them in the promotion play-offs. One year later,
Bijelo-plavi tried for promotion again, winning in a penalty shoot-out against
Rijeka, but end up being stopped by
Vardar. The next time Osijek reached the promotion play-offs was in 1973. It went to the final round, beating
FC Prishtina. Following their victory, NK Osijek was set to meet
NK Zagreb at
Stadion Maksimir in
Zagreb. A record-breaking 64,129 tickets were sold with approximately 20,000 of them going to Osijek supporters. NK Zagreb proved victorious on the day, winning via a penalty shoot-out following a 2–2 draw after 90 minutes, Osijek denied promotion for a third time in four years.
1977–1991 In 1977, NK Osijek finally secured its return to the top flight by taking out the league championship. It eventually stayed competitive in the Yugoslav League up until the
Croatian War of Independence, except for the season of 1979–80, when Osijek fought back into the premier league after failing to stay in it. The club was present in the second part of the First League ladder in the 80s, except for 1984, when the team placed sixth, headed by
Davidović,
Lulić,
Džeko,
Lepinjica, Rakela,
Karačić and team captain
Kalinić. In 1989, the team placed eighth with
Davor Šuker leading the line for the side scoring 18 goals, taking out the league's best goalscorer award. Šuker is the only player in NK Osijek history to take out the award. During the last season of the YFL, NK Osijek finished ninth.
1992–1999 After the
dissolution of
SFR Yugoslavia, the
Croatian First Football League was formed and the first season was played in 1992. Due to the war, it was a shortened season played from February to June. NK Osijek was unable to play in Osijek due to the war, so they had to play in the cities of
Đakovo,
Donji Miholjac and
Kutjevo. Osijek finished the
1992 Croatian First League season in 3rd placed, six points behind NK Zagreb and nine behind league champions
Hajduk Split. Osijek's top goalscorer was
Robert Špehar, who finished the season with nine goals. NK Osijek quickly became one of the top four Croatian football teams, with one of its best ever seasons came in the
1994–95. The
Bijelo plavi finished in third place, only six points behind first-placed Hajduk. Špehar scored 23 goals to become the league's top goalscorer. The greats of NK Osijek during that time were–a part from Špehar–Žitnjak, Lulić, Beljan,
Ergović, Rupnik, Beširević, Bičanić and Labak. As a result of the third-placed finish, NK Osijek qualified for the
1995–96 UEFA Cup. It faced
Slovan Bratislava in the preliminary round, going down 6–0. Osijek finished third in the
1997–98 Croatian First League, qualifying for the
1998–99 UEFA Cup. Osijek came up against
Anderlecht. After a famous 3–1 victory at home in front of 15,000 supporters, Osijek lost 2–0 in Belgium and were knocked-out on away goals. In 1998–99, Osijek attained its first trophy, the
Croatian Cup, following a victory over
Cibalia 2–0. One year later,
West Ham United was playing away in Gradski vrt, headed by
Frank Lampard,
Rio Ferdinand,
Trevor Sinclair,
Paolo Di Canio,
Paulo Wanchope and
Igor Štimac.
2000–2015 In the
2000–01 UEFA Cup, NK Osijek beat
Brøndby 2–1 (2–1, 0–0) and
Rapid Wien 4–1 (2–1, 2–0). In the 3rd round, Osijek beat
Slavia Prague 2–0 at home, but lost 5–1 in
Prague. Osijek finished third in the league once more. In the
2001–02 UEFA Cup, Osijek progressed past
Dinaburg on away goals, beat
Gorica in the first round, but then lost 3–5 to
AEK Athens. In the
2003–04 HNL, Osijek had the first and second highest goalscorers in the division with Špehar scoring 18 and
Goran Ljubojević scoring 16. The club then went through a long phase of mid-table finishes and mediocre results. NK Osijek was almost relegated during the
2013–14 season. On the final match day,
Josip Barišić eventually scored and keep Osijek afloat against
Hrvatski dragovoljac. Osijek changed coaches on four occasions throughout the season. The following season, Osijek once again finished one position above the relegation play-off spot, finishing one point ahead of
Istra 1961.
2015–present In September 2015,
Zoran Zekić was appointed as the first team head coach, replacing
Dražen Besek. With the club facing
bankruptcy, Osijek went into
private ownership for the first time in its history in February 2016 with Hungarian
oligarch Lőrinc Mészáros and Croatian
entrepreneur Ivan Meštrović buying a majority of shares in the club. The duo went about stabilizing the club, improving the squad and bringing back ambition to the city and supporters. Much of the debt was restructured and paid off, securing the short-term and long-term future of Osijek. On 27 February 2017, the club celebrated its 70th anniversary in the
Osijek theater. In the
2016–17 season, Osijek finished fourth, which was their highest league finish in nearly 10 years. The 4th-place finish led to Osijek participating in the
qualifying phase of the 2017–18 UEFA Europa League; with the club staging an extremely successful run to the
play-off round, beating
Santa Coloma,
Luzern and
PSV, the former
champions of Europe, who won the 1987–88 edition. The club ended its unbeaten run following a 1–2 home loss against
Austria Wien, and despite the club winning the second leg 1–0, Osijek were eliminated on the
away goals rule. Despite being eliminated, Osijek were praised and congratulated by Croatian press, fans and media for their historic run. In the
2017–18 season, Osijek finished 4th again, securing a place in the UEFA competition. Osijek beat
Petrocub Hîncești 2–1 at home after a draw the first leg in Moldova 1–1, and faced Rangers in the
second qualifying round of the 2018–19 UEFA Europa League. Osijek lost the home leg 1–0. After a bad start to the
2020–21 season, during which Osijek managed only a single point after the first three games of the season, manager
Ivica Kulešević was sacked. On 5 September 2020, Osijek appointed
Nenad Bjelica as the new club manager. On 9 September 2020, it was announced that Lőrinc Mészáros was no longer the formal co-owner of the club, with the private investment fund BETA taking over his shares in NK OS d.o.o. The reason being that Mészáros was also the owner of
Puskás Akadémia FC, and UEFA rules forbade two clubs owned by the same person from participating in European competitions, should they have both qualified. The heaviest defeat in NK Osijek’s history in the
Croatian First Football League occurred on 4 April 2026, when the club lost 0–7 to
GNK Dinamo Zagreb in the 28th round of the
2025–26 SuperSport HNL. This result marked Osijek’s worst league defeat in the modern Croatian league era. ==Stadium==