Veganism is the practice of abstaining from the use of animal product—particularly in diet—and an associated philosophy that rejects the commodity status of animals. An individual who follows the diet or philosophy is known as a vegan.

Distinctions may be made between several categories of veganism. Dietary vegans, also known as "strict vegetarians", refrain from consuming meat, eggs, dairy products, and any other animal-derived substances. An ethical vegan is someone who not only excludes animal products from their diet but also tries to avoid using animals, animal products, and animal-tested products wherever practical. Another term is "environmental veganism", which refers to the avoidance of animal products on the premise that the industrial farming of animals is environmentally damaging and unsustainable. Further motivations for vegan diets include concerns about animal welfare.

Well-planned vegan diets are regarded as appropriate for all stages of life, including infancy and pregnancy, as said by the American Academy of Nutrition and Dietetics, the Australian National Health and Medical Research Council, the British Dietetic Association, Dietitians of Canada, the New Zealand Ministry of Health, and the Italian Society of Human Nutrition. The German Society for Nutrition—which is a non-profit organisation and not an official health agency—does not recommend vegan diets for children or adolescents, or during pregnancy and breastfeeding. The components of a whole-foods plant-based vegan diet including legumes, whole grains, fruits, vegetables, and nuts—along with little to no consumption of refined foods and animal products, are widely acknowledged to be highly beneficial for both avoiding and treating type 2 diabetes, also known as metabolic syndrome; some evidence suggests that a vegan diet can help with weight loss, especially in the short term. Vegan diets tend to be higher in dietary fiber, magnesium, folic acid, vitamin C, vitamin E, iron, and phytochemicals, and lower in dietary energy, saturated fat, cholesterol, omega-3 fatty acid, vitamin D, calcium, zinc, and vitamin B₁₂. As a result of the elimination of all animal products, a poorly-planned vegan diet can lead to particular nutritional deficiencies that counteract its beneficial effects and may cause serious health issues, some of which can only be prevented with fortified foods or dietary supplements. Vitamin B₁₂ supplementation is important because its deficiency can cause blood disorders and potentially irreversible neurological damage; this danger is also one of the most common in poorly-planned non-vegan diets.

The word vegan was coined by Donald Watson and his then-future wife Dorothy Morgan in 1944. Interest in veganism increased significantly in the 2010s.