The supporters of Celtic FC, a Scottish football club, were estimated in 2003 to number around 12 million worldwide. Numerous fan magazines and supporters' websites are dedicated to the club, and there are in excess of 800 supporters' clubs in over 60 countries around the world.

Celtic supporters have traditionally come from the Catholic population of Scotland and people of Irish background, but not exclusively. In 2003, Celtic fans received awards from FIFA and UEFA for their exemplary fair and cordial conduct after 80,000 fans had travelled to Seville for the 2003 UEFA Cup final. In 2017, Celtic fans were awarded with the FIFA Fan Award for their tifo commemorating the 50th anniversary of the club's 1967 European Cup win.

Famous fans

Jay Baruchel, Canadian actor Finn Bálor, Irish professional wrestler Norman Blake, lead singer of Teenage Fanclub Frankie Boyle, Scottish stand-up comedian Susan Boyle, Scottish singer Stuart Braithwaite, guitarist in Scottish post-rock band, Mogwai. Kevin Bridges, Scottish stand-up comedian Alison Brie, American actress Charlie Burchill, lead guitarist and founding member of Simple Minds Gerard Butler, Scottish actor Lewis Capaldi, Scottish singer-songwriter Joe Coffey, Scottish professional wrestler Mark Coffey, Scottish professional wrestler Wolfgang, Scottish professional wrestler Billy Connolly, Scottish stand-up comedian and actor Martin Compston, Scottish actor Tony Curran, Scottish actor Lana Del Rey, American singer-songwriter Dominik Diamond, Scottish presenter and newspaper columnist Robert Downey Jr., American actor Francis Dunnery, English musician, singer-songwriter, and record producer Siobhan Fahey, Irish singer Kirsty Gallacher, Scottish journalist Liam Gallagher, English singer and frontman of Oasis Noel Gallagher, English musician and member of Oasis George Galloway, British politician Chris Geddes, keyboardist and founding member of Belle and Sebastian Karen Gillan, Scottish actress Bobby Gillespie, lead singer of Primal Scream Stephen Graham, English actor Clare Grogan, actress and singer Kevin Guthrie, Scottish actor Jon Hamm, American actor Fran Healy, lead singer of Travis Ariel Helwani, Canadian journalist John Higgins, snooker player Jay-Z, American rapper Richard Jobson, Scottish filmmaker, television presenter, and lead singer of punk band Skids Robbie Keane, Irish footballer Roy Keane, Irish footballer. Michelle Keegan, English actress Jim Kerr, lead singer and founding member of Simple Minds CM Punk, American professional wrestler Sami Zayn, Canadian professional wrestler Rory Kinnear, English actor Declan Michael Laird, actor Jenny Lewis, American musician Noah Lomax, American actor Shane Long, Irish footballer Jennifer Love Hewitt, American actress Tony Lundon, Irish singer and former member of Liberty X Johnny Marr, English musician and former guitarist of The Smiths James McAvoy, Scottish actor Ross McCall, Scottish actor James McClean, Irish footballer Aaron McCusker, Northern Irish actor Martine McCutcheon, English singer, TV personality and actress Paul McGinley, Irish golfer Rory McGrath, British comedian Conor McGregor, Irish MMA fighter Eddie McGuire, Australian television presenter and AFL commentator Chris McQueer, Scottish writer and spoken word performer Ilir Meta, President of Albania Mark Millar, Scottish comic book writer and artist Frankie Miller, Scottish singer Gary Mounfield, bassist formerly of The Stone Roses and currently of Primal Scream Kevin Nolan, English footballer and manager Paolo Nutini, Scottish singer Brendan O'Carroll, Irish actor and comedian. Daniel Portman, Scottish actor Johnathan Rice, Scottish-American singer-songwriter Brendan Rodgers, Northern Irish football manager and former player Wayne Rooney, English footballer Tony Roper, Scottish actor, comedian and writer Duke Roufus, American former kickboxer Sheamus, Irish professional wrestler Trevor Sinclair, English footballer Snoop Dogg, American rapper Sharleen Spiteri, lead singer of Texas Rod Stewart, English singer Lawrence Tynes, Scottish-born former American football player The View, Scottish indie rock band Christoph Waltz, Austrian-German actor Humza Yousaf, former First Minister of Scotland

Fanbase Celtic was founded as a charity for poor Irish immigrants in Glasgow by Brother Walfrid, a Marist Brother originally from County Sligo, Ireland. Consequently, Celtic is strongly associated with Scotland's Irish Catholic community and have a significant number of supporters in Ireland and among members of the Irish diaspora elsewhere.

Worldwide

Celtic has developed a fanbase in a number of countries around the world, with over 800 supporters' clubs in over 60 countries around the world.The North American Federation of Celtic Supporters Clubs lists some 125 clubs and the Association of Irish Celtic Supporters Clubs 40 more Research in 2003 by Capita Consulting in conjunction with the Cranfield Institute estimated the worldwide fan base as being around nine million.

There are Celtic supporters clubs in South Korea, Sweden Croatia, Germany, Denmark and Norway while the club's profile in Kenya has been boosted by a team in Nairobi, Kibera Celtic, who were inspired by Celtic's charitable roots and use the profits from football to fund charitable initiatives in Kenya and throughout Africa. This fanbase extended to Japan in 2005, when Japanese international Shunsuke Nakamura joined the club, although the Tokyo Celtic Supporters' Club had already been established in 2001.

In 2003, it was estimated that Celtic had a fanbase of one million in the United States and Canada. In 2002, former Rangers director, Hugh Adam, claimed that Celtic were "the best-supported football club in North America" and that the club's "Irish connection" was a determinant factor in their popularity.Adam shakes Ibrox pillars with warning of bankruptcy The Scotsman. 2 February 2002. Retrieved 7 August 2011. In 2004, The Sunday Times, when commentating on several European teams who were touring in the U.S. at the time, stated that clubs such as Chelsea, Real Madrid and Manchester United attracted support in the United States only when touring the country. In contrast, Celtic were said to "have such a strong pre-existing relationship with a huge expatriate following here that their support will endure." There are around 80 Celtic supporters clubs in North America, and nearly half of all U.S. states have a Celtic supporters club.

Celtic have also developed supporters clubs in Australia, South Africa, and elsewhere in the Southern Hemisphere.

Attendance

Celtic's home stadium is Celtic Park, located in Parkhead in the East End of Glasgow. It is the sixth largest stadium in the United Kingdom and the largest football stadium in Scotland. Celtic Park's capacity has been 60,832 since the mid-1990s following redevelopment that turned it into an all-seater stadium, then in 2002 was put down to 60,501 then in 2003 until the present 2013–14 season put down again to 60,355.

Celtic Park's average attendance for the 2010–11 season was 48,968, the highest in Scottish football and the twelfth highest in Europe. Celtic's highest average attendance over the last ten seasons was 58,150 in the 2005–06 season. Over the next three seasons Celtic's average attendance remained above 57,000 before dropping to 45,582 during the 2009–10 season. A study of stadium attendance figures from 2013 to 2018 by the CIES Football Observatory ranked Celtic at 16th in the world during that period, with the proportion of the distribution of spectators in Scotland at 36.5%, the highest of any club in the leagues examined (Rangers were not far behind at 18th place globally and 27.4% of national audience share).

The Scottish Cup final in 1937 between Celtic and Aberdeen at Hampden Park was watched by a crowd of 146,433, which is a record for a club match in Europe. In 1970, Celtic's 'home' leg of their two-legged European Cup semi-final tie against Leeds United was played at Hampden Park to accommodate the expected large attendance. A 136,505 crowd watched Celtic win 2–1 on the night, a record attendance for a competitive European club tie that stands to this day.

The club's large travelling support make Celtic a popular choice of opponent for English-based footballers to select for testimonial matches. Over 5000 Celtic supporters turned for Peter Beardsley's testimonial match at St James' Park, Newcastle, in January 1999. An estimated 15,000 Celtic supporters attended at Old Trafford for the testimonials of Bryan Robson in November 1990 and for Ryan Giggs in August 2001.

2003 UEFA Cup final

In 2003, Celtic reached the UEFA Cup final, with the match ending 3–2 to FC Porto. An estimated 80,000 Celtic supporters travelled to Seville for the occasion. Celtic fans received awards from UEFA and FIFA for their "loyal and sporting behaviour" at the match. FIFA president Sepp Blatter also praised the Celtic fans when he presented the FIFA Fair Play award at Celtic Park; "I can only say that this is not the first time that Celtic fans have presented themselves as warm and wonderful supporters." The massive travelling support that followed Celtic over to Seville to watch them in the final became known as The Bhoys from Seville.

Old Firm rivalry

Celtic's traditional rivals are Rangers; collectively, the two clubs are known as the Old Firm. The two have dominated Scottish football's history; between them, they have won the Scottish league championship 104 times since its inception in 1890 – all other clubs combined have won 19 championships.

The rivalry between the teams had various ethnic, religious and political associations, in that Celtic are associated with Irish Catholic origins and Rangers with Scotland's Protestant and British Unionist communities. A report prepared for Glasgow City Council in 2003 found that 74% of Celtic supporters described themselves as Roman Catholic and 10% as Protestant. For Rangers supporters, the figures were 5% and 65% respectively.NFO Social Research Sectarianism in Glasgow – Final Report Glasgow City Council, January 2003

"The clubs have attracted the support of opposing factions in the political difficulties of Northern Ireland, which intensified the rivalry in Scotland." Anti-sectarian charity Nil by Mouth notes that some supporters use songs, chants and banners on match days to express abuse or support towards the Protestant or Catholic faiths and proclaim support for Northern Irish-based terrorist groups such as the IRA and UVF. A study in 2008 by the University of Strathclyde found that the Old Firm rivalry was "strongly linked to the conflict in Northern Ireland".

There have been about 400 Old Firm matches played. The games have been described as having an "atmosphere of hatred, religious tension and intimidation which continues to lead to violence in communities across Scotland." The rivalry has fuelled many assaults and even deaths on Old Firm Derby days. Admissions to hospital emergency rooms have been reported to increase ninefold over normal levels and journalist Franklin Foer noted that in the period from 1996 to 2003, eight deaths in Glasgow were directly linked to Old Firm matches, and hundreds of assaults.Foer, pp. 36–37