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Sterilisation (British English) and sterilization (American English) refer to the complete elimination or destruction of all forms of microbial life, including bacteria, viruses, fungi, and spores, on surfaces, instruments, products, or within environments. In practice, sterilization is distinguished from disinfection and sanitization by its goal of achieving sterility under defined conditions and validated processes.

Common methods of sterilization include heat-based, chemical, radiation, and filtration approaches. Moist heat in autoclaves is the most widely used method for many instruments and packs, typically at about 121°C with a pressurized steam cycle for 15 to 20 minutes, though validated times can vary. Dry heat sterilization, used for items that corrode or are sensitive to moisture, generally employs higher temperatures (approximately 160–180°C) for longer periods. Chemical sterilants are applied to heat-sensitive devices using liquids such as glutaraldehyde or ortho-phthalaldehyde, or through vapor-phase processes. Gas sterilization uses ethylene oxide or hydrogen peroxide plasma for heat- and moisture-sensitive items. Radiation methods include gamma irradiation and electron-beam treatment for packaged goods and single-use medical devices. Filtration can achieve sterilization of liquids or gases through validated pore sizes, though it does not inactivate all viruses or spores in every context.

Validation and quality assurance are essential elements, involving process indicators, routine monitoring, and biological indicators (such as spore tests) to verify lethality. A sterility assurance level (SAL) of typically 10^-6 is often cited for medical devices, indicating a very low probability of a surviving organism. Packaging, aeration, and material compatibility influence the maintenance of sterility until use. Standards and regulations from ISO, EN, and national bodies guide methods, equipment validation, and safety requirements.

Applications span healthcare facilities, pharmaceutical manufacturing, laboratories, sterile compounding, and the preparation of sterile foods and consumer products, with emphasis on aseptic technique, traceability, and safety.