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Lactic acid is a naturally occurring C 3 α‐hydroxycarboxylic acid that is a product of anaerobic metabolism of sugars in virtually all living things. It is a colorless to slightly yellow, hydroscopic liquid commercially available in 50 – 90 wt % solutions. Lactic acid is made industrially by fermentation of carbohydrates or synthetically via the hydrolysis of lactonitrile. Production by fermentation has increased over the last decade as it produces the highly enantiopure l ‐lactic acid that is needed for food and polymer applications. Historically, foods have been the largest volume application, as lactic acid is a mild‐tasting acidulant and food preservative. The use of lactic acid based polymers has increased significantly since ca. 2002. These polymers have the potential to develop into a million‐tonne industry over the next 20 years. The commercial lactic acid processes use a variety of sugar for raw materials (sucrose from sugar beets and sugar cane, dextrose from corn), depending on price and availability of these sugars near the plant location. There are also a number of purification processes that are used commercially (lactate ester distillation, distillation, liquid – liquid extraction). The article contains sections titled: 1. Introduction 2. Properties 2.1. Physical Properties 2.2. Chemical Properties 2.2.1. Internal Esterification 2.2.2. Esterification 2.2.3. Other Reactions 3. Production 3.1. Lactic Acid Fermentation 3.2. Lactic Acid Purification 3.3. Synthesis of Lactic Acid 3.4. Construction Materials 4. Uses 4.1. Food Uses 4.2. Polymers 4.3. Industrial Uses 5. Quality Specifications 6. Analysis 7. Storage and Transportation 8. Legal Aspects 9. Economic Aspects 10. Environmental Protection 11. Toxicology and Occupational Health