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Bayer AG is a German chemical and pharmaceutical company founded in 1863 by Friedrich Bayer (1825â80), a chemical salesman, and Johann Friedrich Weskott (1821â76), who owned a dye company. Headquartered in Leverkusen, near Cologne, the company employs about 90,000 workers worldwide (2025) and operates in more than 80 countries, with major businesses in pharmaceuticals, consumer health, and crop science.
1863â1912: Founding and early growth
The company, originally based in Barmen (now Wuppertal), was called Friedr. Bayer et comp. and manufactured dyestuffs. In 1881, it was incorporated as Farbenfabriken vormals Friedr. Bayer & Co. Aspirin, the chance invention of Bayer chemist Felix Hoffmann (1868â1946), was introduced by the company in 1899.
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Bayer developed its Leverkusen industrial site in the late 19th and early 20th centuries; it later became the companyâs headquarters.
In the late 19th and early 20th centuries, Bayer expanded its research and production, establishing a pharmaceutical division and growing its international presence. By the early 1900s, the company had subsidiaries in several European countries and the United States. The company derived much of its revenue from exports. During this period Bayer also developed a major industrial site at Leverkusen, which became its headquarters in 1912.
1912â1945: Expansion and IG Farben era
That same year, Carl Duisberg (1861â1935), a chemist, became Bayerâs general director and soon began spearheading the movement that resulted in the consolidation of Germanyâs chemical industries into IG Farben in 1925. Duisberg was IG Farbenâs first chairman. Bayer remained within the cartel until it was dissolved by the Allied authorities after World War II in 1945.
1951â1999: Reestablishment and diversification
In 1951, an independent Bayer was reestablished as Farbenfabriken Bayer Aktiengesellschaft following the dissolution of IG Farben. The current name was adopted in 1972. From 1981 to 1999 Bayer held a controlling interest in the Agfa-Gevaert Group, a German and Belgian producer of photographic equipment and film, magnetic tape, and photocopying and duplicating machines.
2000â2018: Expansion and Monsanto acquisition
Bayer continued to expand its holdings with such notable acquisitions as Schering AG (2006), a German pharmaceutical firm that was the largest maker of birth control pills. In addition, Bayer diversified, establishing a crop science division in 2002. In 2016, Bayer agreed to purchase Monsanto, an American producer of agricultural products, including Roundup, a glyphosate-based herbicide (weed killer). The deal, which was valued at $63 billion, closed in 2018.
2018âpresent: Roundup litigation and restructuring
Shortly after the acquisition closed, a California jury found Monsanto liable in a lawsuit alleging that Roundup caused cancer, particularly non-Hodgkin lymphoma, and the prospect of extensive legal liabilities contributed to a decline in Bayerâs market value. In 2020, the company agreed to pay more than $10 billion to settle thousands of claims regarding the herbicide.
Legal challenges continued into the 2020s. Bayer faced tens of thousands of lawsuits and set aside billions of dollars for settlements and related costs. In 2025, a U.S. jury awarded $2.1 billion in damages in one case, one of the largest verdicts to date.
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An early bottle of Bayer aspirin, sold in powdered form.
Bayer Corporation
In response, the company argued that federal pesticide law preempts state lawsuits over the lack of a cancer warning on Roundup labels because the U.S. Environmental Protection Agency doesnât require such a warning. In 2026, the U.S. Supreme Court ruled 7â2 in Bayerâs favor, holding that federal law preempts those lawsuits, a decision that was expected to block thousands of pending cases. The ruling leaves open other types of claims, such as product-design lawsuits.
Products and innovations
The companyâs trademark, the Bayer cross, is internationally recognized. Scores of pharmaceuticals, dyes, acetates, synthetic rubbers, plastics, fibers, insecticides, and other chemicals were first developed by Bayer.
In addition to being the originator and first marketer of aspirin (1899), Bayer was the first company to mass-produce heroin for use in pain and cough medications (1898). It introduced the first sulfa drug, Prontosil (1935), an early antibiotic, and developed polyurethane (1937), a base material for synthetic foams, paints, adhesives, fibers, and other goods.
