The plant Ocimum gratissimum is well-known from the ancient Indian medicine system. O. gratissimum has wide variety of therapeutic applications. Folk medicine says that it can help with headaches, fevers, diarrhoea, pneumonia, and other ailments. O. gratissimum contains several bioactive constituents widely used as food additives, food colorants, pharmaceuticals, pesticides, and fragrances. This review discusses up to this point data on the phytochemical composition, pharmacological studies of Ocimum gratissimum extracts and oil from numerous locations worldwide. Pertinent data of O. gratissimum was earned from numerous electronic scientific databases, and additional information was obtained from books, thesis and different relevant websites. The yield of the O. gratissimum essential oil (OGEO) varied between 0.12% and 1.66% on a dry basis, depending on the variety, plant parts and extraction methods used. OGEO was predominantly accumulated phenylpropenes, (55.7%-57.3%) followed by sesquiterpenes (27.5%-38.1%), and monoterpenes (4.0%-16.1%). Eugenol, germacrene-D, ocimene, 1,8-cineole, selinene, caryophyllene, murolene, cymene, thymol, terpinene, thujene and myrcene are major constituents of OGEO from various origins. These compounds are chief bioactive substances responsible for pharmacological activities such as antioxidant, antimicrobial, antidiabetic, antiinflammatory, gastrointestinal, insecticidal, and larvicidal activities.