Phytotherapy, phytomedicine, or herbal medicine is a medicinal application of plants’ repertoire of metabolites to substitute or complement conventional therapy with unsatisfactory therapeutic outcomes or evitable adverse effects. Plants are complex chemical industries that produce different phytochemicals/secondary metabolites with diverse structural functionalities and biological effects. Some of these metabolites often provide a modifiable structural framework to develop a series of derivatives or inspire the synthesis or repurposing of drugs. Extensive clinical evaluations are still required to provide robust evidence of the benefits and quality control of the available therapeutic products. Training of prescribers, awareness education or campaigns among the population, and rational or sustainable use of world plant biodiversity remain crucial for the effective application of phytotherapy.