Pasteurisation is the heat treatment of liquids, most famously milk, to destroy harmful microorganisms and extend keeping quality. Named for Louis Pasteur, whose nineteenth-century work on wine spoilage founded the science, it typically uses high-temperature short-time (HTST) treatment: 72 °C for 15 seconds for milk, followed by rapid cooling. This kills vegetative pathogens including Salmonella, Listeria monocytogenes, Campylobacter, and Mycobacterium bovis, the cause of bovine tuberculosis transmitted through raw milk, while preserving flavour and nutrition far better than sterilisation. Extended shelf life (ESL) variants use slightly higher temperatures for longer chilled life. Pasteurisation does not sterilise: spoilage organisms survive, so pasteurised milk still needs refrigeration. It remains one of public health’s greatest victories, virtually eliminating milk-borne tuberculosis, brucellosis, and Q fever where universally applied.