Phytotherapy is the use of extracts from natural origin as medicines or health-promoting agents. Although regarded as "alternative medicine" by much of Western medicine, phytotherapy, when critically carried out, is an important field of pharmacognosy.

Phytotherapy relies on the use of plants either whole or in the form of prepared extracts and essences. For thousands of years, plants were a primary source of therapeutic medication for cultures all over the world. With the 20th century came the development of synthesization techniques and totally synthetic drugs, causing phytotherapy to fall out of popularity. However, plants still have a very important place in medicine, and they will continue to do so well into the foreseeable future.

This technique involves the study of plants to determine their properties, and the careful application of plants to treat medical problems. Herbal medicine is a form of phytotherapy, and many of the remedies used in homeopathy are also phytotherapeutic in origin. Extracts of plants are also used in the preparation of some commercial pharmaceuticals, as are synthetic drugs which are based on compounds found in plants. Researchers are also constantly studying plants to find new pharmaceutical compounds and potential applications for them.

When phytotherapy is conducted responsibly, the preparations used are standardized, which means that they are grown, harvested, and processed in a way which is designed to create a very reliable and stable dose of active ingredients. Quality and safety are also important issues in phytotherapy. Producers want to make products of high quality and reliability so that practitioners will feel comfortable prescribing them, and patients will feel comfortable using them. Due to the lack of regulation over herbal preparations in many nations, reputable producers must also be able to police themselves to confirm that their products are safe for use.

Practitioners can use phytotherapy in alternative medicine, in which plant products provide the focal point of a course of medical treatment, and also in complementary medicine, which blends more conventional medical practice with the use of methods which are viewed as alternative.

Phytotherapy is not automatically safe simply because it is natural. In fact, many of the products used can be very dangerous when they are not handled properly, or when they are taken by patients for whom they are contraindicated. Patients should always work with a doctor when embarking on any course of medical treatment, and this includes phytotherapeutic approaches to medical issues.

See also Herbal Medicine.