UEFA Champions League

The first time the champions of two European leagues met was in what was nicknamed the 1895 World Championship, when English champions Sunderland beat Scottish champions Heart of Midlothian 5–3. The first pan-European tournament was the Challenge Cup, a competition between clubs in the Austro-Hungarian Empire. Three years later, in 1900, the champions of Belgium, Netherlands and Switzerland, which were the only existing leagues in continental Europe at the time, participated in the Coupe Van der Straeten Ponthoz, thus being dubbed as the "club championship of the continent" by the local newspapers.

The Mitropa Cup, a competition modelled after the Challenge Cup, was created in 1927, an idea of Austrian Hugo Meisl, and played between Central European clubs. In 1930, the Coupe des Nations (lit. 'Nations Cup'), the first attempt to create a cup for national champion clubs of Europe, was played and organised by Swiss club Servette. Held in Geneva, it brought together ten champions from across the continent. The tournament was won by Újpest of Hungary. Latin European nations came together to form the Latin Cup in 1949.

After receiving reports from his journalists over the highly successful South American Championship of Champions of 1948, Gabriel Hanot, editor of L'Équipe, began proposing the creation of a continent-wide tournament. In interviews, Jacques Ferran (one of the founders of the European Champions Cup, together with Gabriel Hanot), said that the South American Championship of Champions was the inspiration for the European Champions Cup. After Stan Cullis declared Wolverhampton Wanderers "Champions of the World" following a successful run of friendlies in the 1950s, in particular a 3–2 friendly victory against Budapest Honvéd, Hanot finally managed to convince UEFA to put into practice such a tournament. It was conceived in Paris in 1955 as the European Champion Clubs' Cup.

The first European Cup took place during the 1955–56 season. Sixteen teams participated (some by invitation): AC Milan (Italy), AGF Aarhus (Denmark), Anderlecht (Belgium), Djurgården (Sweden), Gwardia Warszawa (Poland), Hibernian (Scotland), Partizan (Yugoslavia), PSV Eindhoven (Netherlands), Rapid Wien (Austria), Real Madrid (Spain), Rot-Weiss Essen (West Germany), Saarbrücken (Saar), Servette (Switzerland), Sporting CP (Portugal), Reims (France) and Vörös Lobogó (Hungary).

The first European Cup match took place on 4 September 1955, and ended in a 3–3 draw between Sporting CP and Partizan. The first goal in European Cup history was scored by João Baptista Martins of Sporting CP. The inaugural final took place at the Parc des Princes between Stade de Reims and Real Madrid on 13 June 1956. The Spanish squad came back from behind to win 4–3 thanks to goals from Alfredo Di Stéfano and Marquitos, as well as two goals from Héctor Rial. Real Madrid successfully defended the trophy next season in their home stadium, the Santiago Bernabéu, against Fiorentina. After a scoreless first half, Real Madrid scored twice in six minutes to defeat the Italians. In 1958, Milan failed to capitalise after going ahead on the scoreline twice, only for Real Madrid to equalise. The final, held in Heysel Stadium, went to extra time where Francisco Gento scored the game-winning goal to allow Real Madrid to retain the title for the third consecutive season.

In a rematch of the first final, Real Madrid faced Stade Reims at the Neckarstadion for the 1959 final, and won 2–0. West German side Eintracht Frankfurt became the first team not to compete in the Latin cup to reach the European Cup final. The 1960 final holds the record for the most goals scored, with Real Madrid beating Eintracht Frankfurt 7–3 at Hampden Park, courtesy of four goals by Ferenc Puskás and a hat-trick by Alfredo Di Stéfano. This was Real Madrid's fifth consecutive title, a record that still stands today.

Real Madrid's reign ended in the 1960–61 season when bitter rivals Barcelona dethroned them in the first round. Barcelona were defeated in the final by Portuguese side Benfica 3–2 at the Wankdorf Stadium. Reinforced by Eusébio, Benfica defeated Real Madrid 5–3 at the Olympic Stadium in Amsterdam and kept the title for a second consecutive season. Benfica wanted to repeat Real Madrid's successful run of the 1950s after reaching the showpiece event of the 1962–63 European Cup, but a brace from Brazilian-Italian José Altafini at Wembley gave the spoils to Milan, making the trophy leave the Iberian Peninsula for the first time ever.

Inter Milan beat an ageing Real Madrid 3–1 at the Ernst-Happel-Stadion to win the 1963–64 season and replicate their local-rival's success. The title stayed in Milan for the third year in a row after Inter beat Benfica 1–0 at their home ground, the San Siro. Under the leadership of Jock Stein, Scottish club Celtic beat Inter Milan 2–1 in the 1967 final to become the first British club to win the European Cup. The Celtic players that day, all of whom were born within 30 miles (48 km) of Glasgow, subsequently became known as the "Lisbon Lions".

The 1967–68 season saw Manchester United become the first English team to win the European Cup, beating two-times winners Benfica 4–1 in the final. In the 1968–69 season, Ajax became the first Dutch team to reach the European Cup final, but they were beaten 4–1 by Milan, who claimed their second European Cup, with Pierino Prati scoring a hat-trick.

The 1969–70 season saw the first Dutch winners of the competition. Feyenoord knocked out the defending champions, Milan in the second round, before beating Celtic in the final. In the 1970–71 season, Ajax won the title, beating Greek side Panathinaikos in the final. the season saw a number of changes, with penalty shoot-outs being introduced, and the away goals rule being changed so that it would be used in all rounds except the final. It was also the first time a Greek team reached the final, as well as the first season that Real Madrid failed to qualify, having finished sixth in La Liga the previous season. Ajax went on to win the competition three years in row (1971 to 1973), which Bayern Munich emulated from 1974 to 1976.

The era was characterized by the dominance of football clubs from the Netherlands and West Germany, who together won 7 back-to-back European Cups between 1970 and 1976.

Liverpool won their first two titles in 1977 and 1978. The following seasons saw victories in 1978–79 and 1979–80 for Brian Clough's Nottingham Forest. The following year Liverpool won their third title before Aston Villa continued the sense of English dominance in 1982. In 1982–83, Hamburger SV broke the English dominance. Liverpool regained it in 1983–84 before losing to Juventus (1984–85). All English clubs were banned for five years (Liverpool for six years) following the 1985 European Cup final due to the Heysel Stadium disaster.

Following the five-year ban on English teams, Steaua București won the European Cup in 1985–86, followed by Porto in 1986–87, PSV Eindhoven in 1987–88; AC Milan (2), Red Star Belgrade and Barcelona became champions before the competition was re-formulated as the UEFA Champions League. The 1996-97 season was the final Champions League tournament in which European league champions were only allowed to compete; the tournament was won by Borussia Dortmund.

The era was characterized by the dominance of football clubs from England between 1977 and 1984, winning seven European Cup finals, and later the dominance of Italian football clubs in the 1990s; in a nine-year period from 1989 to 1998, Italian clubs reached nine Champions League finals.

The era was characterized by the dominance of football clubs from Spain, who dominated the competition in 1998–2002 and again from 2014–18, with Real Madrid winning three back-to-back Champions League titles in 2016, 2017, and 2018, followed by the dominance of English football clubs between 2005–12 and again from 2018–23. Since the expansion of the Champions League in 1997–98, Spanish clubs reached 17 finals and English clubs reached 16 finals.

During the 2020 COVID-19 pandemic, the tournament was suspended in mid-March 2020 and resumed in August 2020.