Fruitarianism (/fruːˈtɛəriənɪzəm/) is a diet that consists primarily of consuming fruits and possibly nuts and seeds, but without any animal products. Fruitarian diets are subject to criticism and health concerns.

Fruitarianism may be adopted for different reasons, including ethical, religious, environmental, cultural, economic, and presumed health benefits. A fruitarian diet may increase the risk of nutritional deficiencies, such as reduced intake of vitamin B12, calcium, iron, zinc, omega-3 or protein.

Some fruitarians will eat only what falls naturally from a plant; that is, plant foods that can be harvested without killing or harming the plant. These foods consist primarily of culinary fruits, nuts, and seeds. Some do not eat grains, believing it is unnatural to do so,^{[citation needed]} and some fruitarians feel that it is improper for humans to eat seeds as they contain future plants, or nuts and seeds, or any food besides juicy fruit. Others believe they should eat only plants that spread seeds when the plant is eaten. Others eat seeds and some cooked foods. Some fruitarians use the botanical definitions of fruits and consume pulses, such as beans, peas, or other legumes. Other fruitarians' diets include raw fruits, dried fruits, nuts, honey and olive oil, nuts, beans or chocolate.

A related diet is nutarianism, for individuals who only eat nuts.

Some fruitarians, like Jains, wish to avoid killing anything, including plants, and refer to ahimsa fruitarianism. For some fruitarians, the motivation comes from a fixation on a utopian past, their hope being to return to a past that pre-dates an agrarian society to when humans were simply gatherers. Another common motivation is the desire to eliminate perceived toxicity from within the body. For others, the appeal of a fruitarian diet comes from the challenge that the restrictive nature of this diet provides.

According to nutritionists, adults must be careful not to follow a fruit-only diet for too long. A fruitarian diet is wholly unsuitable for children (including teens), nursing mothers and their babies. Death can result from malnutrition.

Fruitarianism is more restrictive than veganism or raw veganism, as a subset of both. Maintaining this diet over a long period can result in dangerous deficiencies, a risk that many fruitarians try to ward off through nutritional testing and vitamin injections. The Health Promotion Program at Columbia University reports that a fruitarian diet can cause deficiencies in calcium, protein, iron, zinc, vitamin D, most B vitamins (especially B₁₂), and essential fatty acids.

Although fruit provides a source of carbohydrates, they have very little protein, and because protein cannot be stored in the body as fat and carbohydrates can, fruitarians need to be careful that they consume enough protein each day. When the body does not absorb enough protein, it leads to a deficiency of amino acids, which are essential to creating body proteins which support the growth and maintenance of body tissues. Consuming high amounts of fruit also poses a risk to those who are diabetic or pre-diabetic, due to the negative effect that the large amounts of sugar in fruits has on blood sugar levels. These high levels of sugar mean that fruitarians are at a higher risk for tooth decay. Another concern that fruitarianism presents is that because fruit is easily digested, the body burns through meals quickly, and is hungry again soon after eating. A side effect of the digestibility is that the body will defecate more frequently. Additionally, the Health Promotion Program at Columbia reports that food restrictions in general may lead to hunger, cravings, food obsessions, social disruptions, and social isolation. The severe dietary restrictions inherent in a fruitarian regime also carries the serious risk of triggering orthorexia nervosa.