Ocimumtenuiflorum (synonym Ocimum sanctum), commonly known as holy basil, is an aromatic perennial plant in the family Lamiaceae. It is native to the Indian subcontinent and widespread as a cultivated plant throughout the Southeast Asian tropics.

Tulsi is cultivated for religious and traditional medicine purposes, and for its essential oil. It is widely used as a herbal tea, commonly used in Ayurveda, and has a place within the Vaishnava tradition of Hinduism, in which devotees perform worship involving holy basil plants or leaves.

Holy basil is an erect, many-branched subshrub, 30–60 cm (12–24 in) tall with hairy stems. Leaves are green or purple; they are simple, petioled, with an ovate, up to 5 cm (2.0 in)-long blade which usually has a slightly toothed margin; they are strongly scented and have a decussate phyllotaxy. The purplish flowers are placed in close whorls on elongate racemes. The two main morphotypes cultivated in India and Nepal are green-leaved (Sri or Lakshmi tulasi) and purple-leaved (Krishna tulasi).

Chemical composition
Some of the phytochemical constituents of tulsi are oleanolic acid, ursolic acid, rosmarinic acid, eugenol, carvacrol, linalool, β-caryophyllene (about 8%).
Tulsi essential oil consists mostly of eugenol (~70%) β-elemene (~11.0%), β-caryophyllene (~8%) and germacrene (~2%), with the balance being made up of various trace compounds, mostly terpenes.