Ocimum tenuiflorum, commonly known as holy basil, tulasi or tulsi (from Sanskrit), is an aromatic perennial plant in the family Lamiaceae.

It is widely used as an 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.

Leaves are green or purple; they are simple, petioled, with an ovate blade up to 5 cm (2 in) long, which usually has a slightly toothed margin; they are strongly scented and have a decussate phyllotaxy.

[8] The plant and its oil contain diverse phytochemicals, including tannins, flavonoids, eugenol, caryophyllenes, carvacrol, linalool, camphor, and cinnamyl acetate, among others.

[12] However, other studies have stated tulsi essential oil consists mostly of eugenol (70%) β-elemene (11%), β-caryophyllene (8%), and germacrene (2%), with the balance being made up of various trace compounds, mostly terpenes.

[21] The essential oil may have nematicidal properties against Tylenchulus semipenetrans, Meloidogyne javanica, Anguina tritici, and Heterodera cajani.

During the Kati Bihu festival celebrated in Assam, people light earthen lamps (diya) at the foot of the household tulsi plants and pray.