Animal testing, also known as animal experimentation, animal research, and in vivo testing, is the use of non-human animals in experiments that seek to control the variables that affect the behavior or biological system under study. This approach can be contrasted with field studies in which animals are observed in their natural environments. Experimental research with animals is usually conducted in universities, medical schools, pharmaceutical companies, defense establishments, and commercial facilities that provide animal-testing services to industry. The focus of animal testing varies on a continuum from pure research, done with little regard to the uses to which understanding may be put, to applied research, which may focus on answering some question of great practical importance, such as finding a cure for a disease. Examples of applied research include testing, breeding, defense research, and toxicology, including cosmetics testing). In education, animal testing is sometimes a component of biology or psychology courses. The practice is regulated to varying degrees in different countries.

Animals used by laboratories for testing purposes are largely supplied by dealers who specialize in selling them to universities, medical and veterinary schools, and companies that provide contract animal-testing services. It is comparatively rare that animals are procured from sources other than specialized dealers, as this poses the threat of introducing disease into a colony and confounding any data collected. However, suppliers of laboratory animals may include breeders who supply purpose-bred animals, businesses that trade in wild animals, and dealers who supply animals sourced from pounds, auctions, and newspaper ads. Animal shelters may also supply the laboratories directly. Some animal dealers, termed Class B dealers, have been reported to engage in kidnapping pets from residences or illegally trapping strays, a practice dubbed as bunching.