Bayer 04 Leverkusen is a German professional football club founded in 1904 as a sports section for employees of the Bayer chemical company, whose plant still dominates the Rhineland town of Leverkusen. The club plays at the BayArena, a compact ground of roughly 30,000 seats, and its factory origins gave rise to the nickname Die Werkself, "the works eleven".

Leverkusen won the UEFA Cup in 1988 and the DFB-Pokal in 1993, but for decades was better known for near misses, most famously in 2002 when it finished runner-up in the Bundesliga, DFB-Pokal and Champions League in a single season. That reputation was overturned in 2023-24, when the side went unbeaten through the domestic season to claim its first Bundesliga title and the German double. It competes in the Bundesliga.