UEFA Champions League was introduced back in 1955 as “European Cup” where only the league champions of european leagues were invited to play in knockout only tournament. Real Madrid went on to win first 5 European cup. Tournament was rebranded in 1992 as “Champions League”. 2nd, 3rd and 4th placed teams in top european league were included in group format tournament which stands to this day.
So when looking at most successful teams in tournaments history we must see european cup and champions league as different tournaments. We can name them as “European Cup Era” and “Modern Era”
European Cup Era: First introduced as European Cup as knockout only tournament where only the champions of european leagues were invited. That was one of the reason competition lacked competitive edge as champions of top european leagues dominated the tournament. Real Madrid won first 5 back to back tournaments and it was easier to defend the title compared to modern era.
Modern Era: Tournament was rebranded as “UEFA Champions League” in 1992 where group phase was introduce and 2nd, 3rd and 4th place teams from top european leagues were invited. Since 1992 only Real Madrid have manage to defend the title which happened when they won three back to back titles from 2016 to 2018.
Most Successful Teams in competitions history:
Real Madrid with 13 titles to date is the most successful team in competitions history. They won 6 titles in European cup era and another 7 in modern era. AC Milan have won the tournament on 7 separate occasions while Bayern Munich and Liverpool have won the competitions 6 times each.
| TEAMS | European Cup Era | Modern Era | TOTAL |
|---|---|---|---|
 Real Madrid | 6 titles (1956,57,58,59,60,66) | 7 titles (1998,2000,02,14,16,17,18) | 13 |
 AC Milan | 4 titles ((1963,69,89,90)) | 3 titles (1994,2003,07) | 7 |
 Bayern Munich | 3 titles (1974,75,76) | 3 titles (2001,13,20) | 6 |
 Liverpool | 4 titles (1977,78,81,84) | 2 (2005,19) | 6 |
| FC Barcelona | 0 | 5 titles (1992, 2006,09,11,15) | 5 |
 Ajax | 3 titles (1971,72,73) | 1 title (1995) | 4 |
| Manchester United | 1 title (1968) | 2 titles (1999,2008) | 3 |
| Inter Milan | 2 titles (1964,65) | 1 title (2010) | 3 |
| Juventus | 1 title (1985) | 1 title (1996) | 2 |
 FC Benfica | 2 titles (1961, 62) | 0 | 2 |
| Nottingham Forest | 2 titles (1979,80) | 0 | 2 |
| FC Porto | 1 title (1987) | 1 title (2004) | 2 |
 Celtic | 1 title (1967) | 0 | 1 |
| Hamburg | 1 title (1983 | 0 | 1 |
 Steaua București | 1 title (1986) | 0 | 1 |
 Marseille | 0 | 1 title (1993) | 1 |
| Borussia Dortmund | 0 | 1 title (1997) | 1 |
| Chelsea | 0 | 1 title (2011) | 1 |
| Feyenoord | 1 title (1970) | 0 | 1 |
| Aston Villa | 1 (1982) | 0 | 1 |
| PSV | 1 (1988) | 0 | 1 |
 Red Star Belgrade | 1 (1991) | 0 | 1 |