Inoculation is the act of implanting a pathogen or other microbe or virus into a person or other organism. It is a method of artificially inducing immunity against various infectious diseases. The term "inoculation" is also used more generally to refer to intentionally depositing microbes into any growth medium, as into a Petri dish used to culture the microbe, or into food ingredients for making cultured foods such as yoghurt and fermented beverages such as beer and wine. This article is primarily about the use of inoculation for producing immunity against infection. Inoculation has been used to eradicate smallpox and to markedly reduce other infectious diseases such as polio. Although the terms "inoculation", "vaccination", and "immunization" are often used interchangeably, there are important differences. Inoculation is the act of implanting a pathogen or microbe into a person or other recipient; vaccination is the act of implanting or giving someone a vaccine specifically; and immunization is the development of disease resistance that results from the immune system's response to a vaccine or natural infection.

Artificial induction of immunity is immunization achieved by human efforts in preventive healthcare, as opposed to natural immunity as produced by organisms' immune systems. It makes people immune to specific diseases by means other than waiting for them to catch the disease. The purpose is to reduce the risk of death and suffering, that is, the disease burden, even when eradication of the disease is not possible. Vaccination is the chief type of such immunization, greatly reducing the burden of vaccine-preventable diseases.