Animal testing refers to the use of live animals in experiments or procedures for scientific, medical, cosmetic, educational or regulatory purposes, often in the context of product safety or biomedical research. In UK law, the practice is primarily regulated by the Animals (Scientific Procedures) Act 1986 (ASPA), which requires a project licence, personal licence and establishment licence, and imposes controls on the care, use, pain relief and euthanasia of “protected animals”. The concept overlaps with statutory terms such as “regulated procedures” under ASPA. In Ireland, animal testing is governed by legislation implementing Directive 2010/63/EU, with a similar licensing and inspection regime, and parallel concepts such as “procedures” on protected animals. Across England & Wales, Scotland, Northern Ireland and Ireland, animal testing law is underpinned by the Three Rs (replacement, reduction, refinement) and engages administrative, criminal and regulatory law. The term is significant in advising on compliance, challenging or defending enforcement action, drafting research protocols, procurement and ethics policies, judicial review of licensing decisions, and navigating overlapping regimes on medicines, chemicals, veterinary products and cosmetics.