Bayer 04 Leverkusen was founded on 1 July 1904 by employees of the pharmaceutical and chemical company Bayer AG in the Rhineland town of Leverkusen. The club is uniquely owned by Bayer AG itself — one of the few exceptions to German football's "50+1" rule, which is why Leverkusen, alongside Wolfsburg (Volkswagen), is referred to as a "Werksklub" (works club). The "Werkself" (works eleven) nickname captures this industrial heritage.
Promoted to the Bundesliga in 1979, Leverkusen claimed their first major trophy in 1987-88 with a memorable UEFA Cup victory over Espanyol on penalties. The decades that followed earned them the cruel nickname "Vizekusen" — perpetual runners-up — as the club finished second in the Bundesliga five times without ever winning the title, agonisingly losing the 2002 UEFA Champions League final to Real Madrid (Zinedine Zidane's iconic volley) and the 2002 DFB-Pokal final, all in the same season. Klaus Toppmöller's 2002 squad — Michael Ballack, Lúcio, Bernd Schneider, Yıldıray Baştürk — remains a fan favourite despite the heartbreak.
The drought ended in spectacular fashion in 2023-24 under Xabi Alonso. Leverkusen captured their first-ever Bundesliga title — and did it unbeaten across the entire 34-game league campaign, the first such achievement in Bundesliga history. They added the DFB-Pokal in the same season for a domestic double and reached the UEFA Europa League final. Florian Wirtz, Granit Xhaka, Jeremie Frimpong and Victor Boniface led one of European football's most exciting modern projects. The Rhine Derby against 1. FC Köln and the rivalry with neighbouring Borussia Mönchengladbach are core fixtures.