Stal Mielec, having won the Polish championship twice in the 1970s, earned the right to compete in the European Cup of national champions, where it was drawn against Real Madrid - a match at the club's Solskiego Street stadium in Mielec that drew a crowd of 40,000, a record attendance in the club's history. The club was founded on 10 April 1939 as the football section of the newly established Klub Sportowy PZL Mielec, set up on the initiative of workers at the local aircraft factory, whose ranks were joined by players from other Mielec sides. After the war the club competed under the name RKS PZL 'Zryw' Mielec, and in the 1950s, alongside the growth of the local WSK engineering plant, work began on building a squad with ambitions to compete at the national level, with forward Helmut Tobollik playing a key role, scoring 58 goals in the second tier between 1956 and 1960.
The club's finest era came in the 1970s: on 24 June 1973, thanks to goals from Grzegorz Lato and Jan Domarski, Stal beat Zagłębie Wałbrzych 2-0 to claim its first-ever Polish championship, and three years later, under coach Edmund Zientara, defended the title in a race decided on the final matchday, along the way recording a memorable 6-0 win over Legia Warsaw. In the 1975-76 season the Mielec side also achieved the club's greatest international result, reaching the quarter-finals of the UEFA Cup before losing to Hamburger SV - to this day remaining, alongside Ruch Chorzów, one of only two Polish clubs to have gone that far in the competition. The team at the time featured key Polish internationals, including bronze medallists from the 1974 World Cup in West Germany, with Jan Domarski having scored the goal at Wembley that sent Poland to that tournament.
As defending champions, Stal were drawn against Real Madrid in the first round of the 1976-77 European Cup - a match in Mielec, won by the Spanish side 2-1 through goals from Santillana and Del Bosque, watched by a crowd of 40,000, with club officials rejecting pressure to move the fixture to the Silesian Stadium in Chorzów because of the enormous interest. In the return leg, played in Valencia due to a UEFA ban on Real hosting the match, Mielec lost 0-1 but impressed even Spanish observers with their performance. After years of glory, the club went through both highs and lows, including bankruptcy declared in June 1997 amid financial troubles, after which a reactivated football section took over the entire legacy of the former club. Today, developing some of the country's most talented young footballers through its long-running Grzegorz Lato Sports Championship School, Stal Mielec competes in the Ekstraklasa, playing its home matches at the stadium on Solskiego Street in Mielec.