Longest participation streak in European football competitions

Question

What is the European football team that has the longest consecutive participation streak in the following UEFA club competitions:

• UEFA Champions League (Previously called the European Cup)
• UEFA Europa League (Previously called the UEFA Cup)
• UEFA Cup Winners' Cup (Defunct)

The streak is to be considered valid also if a team has taken part in the UEFA Cup, then the year after in the UEFA Champions League and the year after in the UEFA Cup Winnners' Cup, so each season that a team played a match in the aforementioned UEFA tournaments.

For example, Juventus Turin competed in UEFA competitions for 28 consecutive seasons since 1963 to 1991, more than any other Italian club.

Answer 1

FC Barcelona is the European football team that has the longest consecutive participation streak of 60 (1955/58-2017/18) and counting in UEFA club competitions.

Data from the linked website^{Rec.Sport.Soccer Statistics Foundation} upto season 2015/16:

Consecutive Participations

58 Barcelona (1955/58-2015/16)

52 Anderlecht (1964/65-2015/16)

42 FC Porto (1974/75-2015/16) PSV (Eindhoven) (1974/75-2015/16)

41 Benfica (1960/61-2000/01)

36 Sporting (Lisboa) (1977/78-2012/13)

33 Sparta Praha (1983/84-2015/16)

31 Rangers (1981/82-2011/12)

28 Juventus (1963/64-1990/91)

27 Dynamo Kyiv (1989/90-2015/16)

25 Ajax (1991/92-2015/16)

24 Ajax (1966/67-1989/90) [banned from 1990/91 competition] Crvena zvezda Beograd (1968/69-1991/92) [banned 1992/93 through UN boycott] Spartak Moskva (1980/81-2003/04)
Manchester United (1990/91-2013/14) Olympiakos (Piraeus) (1992/93-2015/16) 23 Levski Sofia (1991/92-2013/14) Bayern München (1993/94-2015/16)

22 Real Madrid (1955/56-1976/77) FC Brugge (1994/95-2015/16)

21 Liverpool (1964/65-1984/85) [banned 1985/86-1991/92 (would have qualified each year)] AEK (Athinai) (1991/92-2011/12)
Celtic (1995/96-2015/16)

20 Austria (Wien) (1976/77-1995/96) Flora Tallinn (1994/95-2013/14) Arsenal (1996/97-2015/16) Partizan Beograd (1996/97-2015/16) 19 Crvena zvezda Beograd (1995/96-2013/14) [banned from 2014/15 competition] Chelsea (1997/98-2015/16) Olympique Lyonnais (1997/98-2015/16) Real Madrid (1997/98-2015/16) Shakhtar Donetsk (1997/98-2015/16)

18 Malmö FF (1964/65-1981/82) Real Madrid (1978/79-1995/96)
Slavia Praha (1992/93-2009/10)

17 Omonia Nicosia (1975/76-1991/92) [withdrew from 1974/75 competition] Besiktas (1984/85-2000/01) Rosenborg BK (Trondheim) (1989/90-2005/06) F91 Dudelange (1999/00-2015/16) Sheriff Tiraspol (1999/00-2015/16)

16 Celtic (1962/63-1977/78) CSKA (Sofia) (1969/70-1984/85)
Internazionale (1976/77-1991/92) Steaua Bucuresti (1984/85-1999/00) Feyenoord (1991/92-2006/07) Skonto Riga (1992/93-2007/08) The New Saints (2000/01-2015/16) FK Ventspils (2000/01-2015/16)

15 Sporting (Lisboa) (1961/62-1975/76) Grasshopper (1970/71-1984/85) Aberdeen (1977/78-1991/92) Dinamo Bucuresti (1981/82-1995/96) Panathinaikos (1998/99-2012/13) Milan (1999/00-2013/14) FC København (2001/02-2015/16)

Answer 2

From European Cup and UEFA Champions League records and statistics:

Consecutive participations

• Real Madrid have the record number of consecutive participations in the European Cup, taking part in the first 15 tournaments from 1955–56 to 1969–70.

• Real Madrid hold the record number of consecutive participations in the UEFA Champions League with 21 from 1997–98 to 2017–18. Arsenal (from 1998–99 to 2016–17) have participated in 19 consecutive campaigns.

From UEFA Cup and Europa League records and statistics #Miscellaneous records:

The record number of consecutive participations in the UEFA Cup/Europa League is 20 by Club Brugge. 1996/97–2015/16

From UEFA Cup Winners' Cup records and statistics #Trivia and records:

It is uncommon for teams to participate in more than two consecutive Cup Winners' Cups, but these teams have done so 5 times:

• Cardiff City (1967–68 + 1971–72)
• Lahti (1973–74 + 1977–78)