Bayer 04 Leverkusen is a German football club based in Leverkusen, North Rhine-Westphalia. It is the most well-known department of TSV Bayer 04 Leverkusen, a sports club whose members also participate in athletics, gymnastics, basketball and other sports.

The team earned a series of top four finishes from 1997 to 2002 that included four second place finishes. The finishes of 2000 and 2002 were heart-breaking for supporters as on both occasions the team had the Bundesliga title within its grasp. In 2000, Bayer Leverkusen needed only a draw against Unterhaching to win the title, but an own goal by Ballack helped send the team to a crushing (0:2) defeat, while Bayern Munich clinched the title with a (3:1) victory over Werder Bremen.

Two years later, the club surrendered a five point lead atop the league table by losing two of its last three matches while Borussia Dortmund swept ahead with three consecutive victories in its final matches. The 2002 season has been dubbed the "Treble Horror", as Bayer Leverkusen were also beaten 4-2 in the German Cup final by Schalke 04, and lost the UEFA Champions League final to Real Madrid by 2 goals to 1. Still, the team earned the honour as the first team ever to reach the UEFA Champions League final without winning a national championship before. They even had to qualify first for the participation in that year's UEFA Champions League.

In contrast to many other German football clubs, which hold close ties to their proletarian roots, Bayer Leverkusen strives for a clean, family-friendly image. The BayArena has the reputation of being one of the most family-friendly football stadiums in Germany.