Ocimum tenuiflorum (also tulsi, tulasī, or Holy Basil) is an aromatic plant in the family Lamiaceae which is native throughout the Old World tropics and widespread as a cultivated plant and an escaped weed.[1] It is an erect, much branched subshrub 30–60 cm tall with hairy stems and simple opposite green leaves that are strongly scented. Leaves have petioles, and are ovate, up to 5 cm long, usually slightly toothed. Flowers are purplish in elongate racemes in close whorls.[2] There are two main morphotypes cultivated in India—green-leaved (Sri or Lakshmi tulsi) and purple-leaved (Krishna tulsi).[3]

Tulsi is cultivated for religious and medicinal purposes, and for its essential oil. It is widely known across South Asia as a medicinal plant and an herbal tea, commonly used in Ayurveda, and has an important role within the Vaishnavite tradition of Hinduism, in which devotees perform worship involving Tulsi plants or leaves.

There is also a variety of Ocimum tenuiflorum which is used in Thai cuisine, and is referred to as Thai holy basil, or kraphao (กะเพรา)[4]—not be confused with "Thai Basil", which is a variety of Ocimum basilicum.