Bausch & Lomb (since 2010 stylized as Bausch + Lomb) is an American-Canadian eye health products company based in Vaughan, Ontario, Canada. It is one of the world's largest suppliers of contact lenses, lens care products, pharmaceuticals, intraocular lenses, and other eye surgery products. The company was founded in Rochester, New York, in 1853 by optician John Bausch and cabinet maker turned financial backer Henry Lomb. Until its sale in 2013, Bausch + Lomb was one of the oldest continually operating companies in the United States.

Bausch + Lomb was a public company listed on the NYSE, until it was acquired by private equity firm Warburg Pincus in 2007. In May 2013, Canadian-based Valeant Pharmaceuticals announced that it would acquire Bausch + Lomb from Warburg Pincus for $4.5 billion in cash. The deal, which was approved by shareholders, closed on August 5, 2013. On May 6, 2022, the company completed an initial public offering and again became publicly traded. As of 2022, the company employs about 12,900 people, and manufactures and markets health care products directly or indirectly in approximately 100 countries.

In 1853, John Bausch and Henry Lomb, both German immigrants, established a small but ambitious workshop producing monocles in Rochester, New York. By 1861, their operation had expanded to manufacturing vulcanite rubber eyeglass frames and other precision vision products.

During the American Civil War, the Union blockade caused the price of gold and European horn to rise dramatically. This resulted in a growing demand for the Bausch + Lomb spectacles made from vulcanite.

In 1876, Ernst Gundlach joined the company as it began to manufacture microscopes. Later that year, the Bausch & Lomb Optical Company won a distinction at the Philadelphia Centennial Exposition. The company also produced photographic lenses (1883), spectacle lenses (1889), microtomes (1890), binoculars and telescopes (1893). From 1892 in cooperation with Zeiss in Germany, the company produced optical lenses. In this manner, at the end of the 19th century, the product range included eyeglasses, microscopes and binoculars, as well as projectors, camera lenses and camera diaphragms.

With the growth of the US army, under President Theodore Roosevelt and the buildup of the naval fleet, Bausch & Lomb received the commission, through the supplier Saegmuller, to manufacture high-precision lenses for optical measurement and founded a joint venture with Saegmuller. At the same time as this new expansion, a research department with five members was started to develop new products and improve old ones. A new alliance with the Zeiss company in Germany ensured competitive advantages for the three participants, Bausch & Lomb, Saegmuller and Zeiss, in terms of patent use and opening new markets. In 1902, William Bausch, the son of the founder, developed a process to create the desired lens shape directly by casting molten glass. Previously, the glass parts for the lenses had to be separated, ground and polished in a complicated process, and this brought significant savings in time and materials.

The company produced the first optical-quality glass in America during the early to mid-1900s. By the year 1903 the company began manufacturing microscopes, binoculars, and camera shutters.

The further development of the firm was affected by political events. Because of the World Wars and the consequent need for optical instruments such as field glasses, range finders, camera lenses, binocular telescopes, searchlight mirrors, torpedo tube sights, and periscopes, the product range could be considerably broadened. Until World War I, optical glass and the instruments made from it (including many military instruments) were often imported into most European and North American countries from Germany. The same was also true of chemical products and laboratory equipment. The outbreak of the war, with Germany's new enemy status, created a scramble to rapidly enhance the domestic industries. In 1933, Bausch + Lomb started to honor outstanding high school science students with the Bausch+Lomb Honorary Science Award. In the 1930s, military products represented 70% of total production. The Ray-Ban brand of sunglasses was developed for pilots in 1936.