Winning the treble is a rarity. It usually happens once or twice in a decade. Eight European clubs, since 1967, have won the treble which includes the European Cup/Champions League and the league title. No club has done it twice, while great clubs like Real Madrid and AC Milan have never completed it.
Celtic FC, 1966-1967
The team known as the Lisbon Lions were the first British club to win the European Cup, beating Inter 2-1 in the Lisbon final. To this date, Celtic are still the only Scottish club to win the trophy. Celtic, under Jock Stein, won a Quintuple that year, including the Scottish League Cup and Glasgow Cup which don’t carry much merit. Another special thing about that team was all the members of this team were born within 30 miles of Glasgow.
AFC Ajax, 1971-1972
The one in between for Ajax, who won three consecutive European Cups. In 1972 Ajax Ajax won their 15th league title and second European Cup, beating Inter 2-0 in the Rotterdam final with two goals from Johan Cruyff. The match is considered the crowning moment of total-football, with Inter desperately defending through the entire affair.
Liverpool, 1983-1984
Liverpool didn’t win the FA Cup that year, just the League Cup, but a Champions League treble is a treble. This one of the most dominant sides in the history of European football, winning its fourth European Cup in the span of 8 seasons, winning the league title six times during that span. Manager Joe Fagan led the team to the win in the final over Roma, in Rome, after a penalty shootout. Ian Rush scored 47 goals during that season.
PSV Eindhoven, 1987-1988
Guus Hiddink’s first tenure with club resulted in three consecutive league titles between 1987-1989, with 1988 being the crowning achievement, winning the Dutch Cup, the league title and the European Cup, beating Benfica after a boring 0-0 draw in Stuttgart and penalty kicks. Hiddink returned to Eindhoven in 2002, winning three more league titles.
Manchester United, 1998-1999
Maybe the most famous treble in European history because of the dramatic ending to the season and of the role the English Premier League took over the years. There was something of a destiny surrounding the club that season – from their two goal comeback against Liverpool in the FA Cup and Ryan Giggs’ goal against Arsenal, to the incredible finish at the Camp Nou against a stunned and better Bayern Munich team.
FC Barcelona, 2008-2009
Guardiola’s first year was simply perfect, winning every possible title by the end of that year, including the European Super Cup, Spanish Super Cup and the Clubs World Cup. Taking over a squad that seemed broken and torn apart a year earlier under Frank Rijkaard. The peak was a 2-0 win over Manchester United in Cristiano Ronaldo’s final game before leaving to Real Madrid. Guardiola’s second Champions League title came against United as well.
FC Internazionale, 2009-2010
Inter needed a special manager to bring back the Champions League title after over 40 years. The football they played wasn’t far from the Catenaccio days. Some say it was worse. But Jose Mourinho brings titles, not favorable critique. And Inter are still the only Italian club to complete the Serie A – Italian Cup – Champions League treble, and so far the last European team to do it.
Bayern Munich, 2012-2013
Possibly the most dominant Treble in European history. Bayern Munich won the Champions League for the fifth time by beating Borussia Dortmund in the final 2-1, and also finished ahead of Dortmund in the Bundesliga by breaking or tying almost every thinkable record. They finished the job by winning the German Cup, beating Stuttgart 3-2 in the final.
FC Barcelona, 2014-2015
The only club to accomplish the league, cup and European Cup/Champions League trophy for a second time, Barcelona finished ahead of Real Madrid in the league for their fifth championship in seven years, beat Athletic Bilbao 3-1 in the Copa Del Rey Final and Juventus 3-1 in the Champions League final as their three major signings of the 2014 summer scored the goals in the final.
There have been four lesser trebles – Goteborg in 1983 with the Swedish League, cup and UEFA Cup; Galatasaray (2000) with the same trophies in Turkey; Liverpool (2001) with the Cup Treble – FA Cup, League Cup and UEFA Cup; Porto, with two league-cup-UEFA/Europa League trebles (2003, 2011).