1. Ajax Amsterdam (2018-2019) The 2018-2019 season will be remembered as one of the most spectacular for Ajax Amsterdam. With a young and dynamic team, Ajax dazzled the football world with its attractive and offensive play. The Dutch side eliminated the giants Real Madrid, the three-time defending UEFA champions, in the Round of 16 with a resounding 4-1 victory at the Santiago Bernabéu. They then defeated Cristiano Ronaldo’s Juventus in the quarter-finals before narrowly falling to Tottenham in the semi-finals due to a last-minute goal by Lucas Moura. Their campaign was praised for its audacity and freshness, reminiscent of Ajax's golden era in the 70s.

2. Leicester City (2016-2017) After improbably winning the Premier League in 2016, Leicester City embarked on its first UEFA Champions League campaign. The Foxes, managed by Claudio Ranieri, surprised everyone by reaching the quarter-finals. They topped their group ahead of Porto, Copenhagen, and Club Brugge, then eliminated Sevilla in the Round of 16. Although they were knocked out by Atlético Madrid, their journey showed that even teams with little European experience could defy expectations.

3. AS Monaco (2016-2017) The 2016-2017 season was also marked by AS Monaco’s remarkable run. Led by young talents such as Kylian Mbappé, Bernardo Silva, and Fabinho, the Monégasques surprised the world by reaching the semi-finals. They eliminated Manchester City in a spectacular Round of 16 tie (6-6 on aggregate, Monaco advancing on away goals) and then defeated Borussia Dortmund in the quarter-finals. Although their journey ended against Juventus in the semi-finals, their offensive play and flair left a lasting impression.

4. FC Porto (2003-2004) Under José Mourinho’s guidance, FC Porto pulled off one of the greatest surprises in UEFA Champions League history in 2003-2004. After winning the UEFA Cup the previous year, Porto continued their momentum by beating Manchester United in the Round of 16 thanks to a dramatic goal by Costinha at Old Trafford. They then eliminated Lyon and Deportivo La Coruña before defeating AS Monaco 3-0 in the final. This triumph propelled Mourinho onto the global stage and proved that underdogs could also dream big.

5. Villarreal CF (2021-2022) Villarreal wrote a memorable chapter in their history during the 2021-2022 season. After winning the Europa League in 2021, the "Yellow Submarine" reached the UEFA Champions League semi-finals for the second time in their history. They eliminated Juventus in the Round of 16 and Bayern Munich in the quarter-finals, significant achievements for a club of their size. Although they were beaten by Liverpool in the semi-finals, their journey was a true fairy tale and showed that mid-sized clubs could compete with the giants.

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1. Nottingham Forest (1978-1980) Nottingham Forest is one of the greatest stories in the history of the UEFA Champions League (then known as the European Cup). Under the legendary manager Brian Clough, Nottingham Forest won the competition twice in a row in 1979 and 1980. What makes this feat even more remarkable is that Forest had just been promoted to the English First Division in 1977. Their unexpected victory proved that even newly promoted teams could conquer Europe with a mix of clever strategy and raw talent.

2. Steaua Bucharest (1985-1986) In 1986, Steaua Bucharest shocked the football world by winning the European Cup. The Romanian team defeated FC Barcelona in the final in Seville, a remarkable achievement for an Eastern European team at the time. Goalkeeper Helmuth Duckadam became a legend by saving four penalty shots in the shootout, allowing his team to lift the trophy. This victory remains one of the biggest surprises in the competition’s history.

3. Red Star Belgrade (1990-1991) Red Star Belgrade, also known as Crvena Zvezda, won the European Cup in 1991, beating Olympique de Marseille in the final. The match ended 0-0 after extra time, and Red Star triumphed 5-3 in the penalty shootout. This success capped an impressive campaign for the Serbian club, which had defeated teams like Bayern Munich in the semi-finals. Their victory showed that Balkan teams could compete with Europe’s best.

3. Hamburger SV (1982-1983) In 1983, Hamburger SV surprised the world by winning the European Cup. Under the management of Ernst Happel, the German club defeated Juventus 1-0 in the final thanks to a goal by Felix Magath. This victory marked the peak of the club's golden era, which also included several Bundesliga titles in the 1980s. The victory against such a strong Italian side as Juventus solidified HSV’s place in European football history.

4. Feyenoord (1969-1970) Feyenoord Rotterdam won the European Cup in 1970, becoming the first Dutch club to win the competition. They defeated Celtic Glasgow 2-1 in the final in Milan. This victory paved the way for a decade of Dutch dominance in Europe, followed by Ajax Amsterdam’s successes in the 1970s. Feyenoord demonstrated that Dutch football could compete with the best teams in Europe.

Also read our article: The History of the UEFA Champions League: From Its Origins to Today

The journey of underdogs in the UEFA Champions League adds an extra dimension of drama and excitement to the competition. These often underestimated teams remind fans that in football, nothing is ever predetermined. Courage, determination, and sometimes a touch of magic can lead improbable teams to unexpected heights, enriching the legacy of the UEFA Champions League and offering football enthusiasts unforgettable stories to tell. On the 1st of June, Dortmund has the opportunity to join these football legends by creating an upset against Real Madrid. Their potential victory would be not only a triumph for the club but also a tribute to the spirit of the underdogs that continue to thrill fans around the world.