Here is a comprehensive summary of the Wikipedia article on Celtic Football Club:

Celtic Football Club, founded in 1887 in Glasgow to alleviate poverty among the city's Irish-Scots population, played its first match in May 1888, defeating Rangers 5–2. After an early period of dominance in the 20th century, the club enjoyed its greatest era under manager Jock Stein in the 1960s-70s, winning nine consecutive league titles and famously becoming the first British team to win the European Cup in 1967. Today, they are a record-breaking global giant, with 56 league championships and 122 major honours—the most of any European club. They share one of the world's most intense derbies, the Old Firm, with Rangers, and boast a massive worldwide following of roughly 9 million fans and over 160 supporters' clubs. A notable moment of this fandom occurred in 2003 when 80,000 supporters traveled to Seville for the UEFA Cup final and, despite defeat, their extraordinary sporting behavior earned the fans FIFA and UEFA Fair Play awards.