Lemongrass (Cymbopogon citratus) is a tall, clumping grass with narrow, tapering leaves, native to the tropical regions of South and Southeast Asia. Its leaves and stalks contain citral, the essential oil responsible for the plant's characteristic citrus fragrance. Its close relative, East Indian lemongrass (Cymbopogon flexuosus), is distilled chiefly for the perfume industry, while the West Indian type used here has long served as a culinary herb. Lemongrass is often confused with the closely related but botanically distinct citronella grass (Cymbopogon nardus or winterianus), whose oil is used chiefly in insect-repellent products.

In Southeast Asian cuisine, particularly Thai and Vietnamese cooking, lemongrass has been an essential ingredient for centuries — a defining flavour of dishes such as tom yum soup. It also plays an important role in the traditional medicine of South and Southeast Asia and in Ayurveda, used to support digestion and calm the mind. Colonial-era trade carried the plant to the Caribbean and East Africa during the 19th century, where it became an established crop. Only more recently has lemongrass also spread worldwide as an incense and aromatherapy material, related to the mosquito-repelling citronella oil. Botanically, lemongrass belongs to the species-rich genus Cymbopogon, which comprises around 55 related grasses, several of which likewise yield fragrant or medicinal oils. The essential oil is obtained by steam distillation of fresh or dried leaves. In Indonesia, the related plant known as "sereh" is just as indispensable in many curries and soups, and in the Western wellness and candle industry, lemongrass has become one of the most popular fragrances of recent decades.

Burned, lemongrass releases a fresh, sharp citrus scent that is invigorating and uplifting. It is valued for freshening a space, clearing the mind, and creating an alert, focused atmosphere. In candles, soaps, and room sprays, lemongrass oil is likewise valued today for its insect-repelling properties. In aromatherapy, lemongrass oil is also credited with a mood-lifting effect, which is why it is frequently blended into diffusers and massage oils for general refreshment. On warm days especially, its scent is often described as particularly invigorating and summery. Combined with other herbal fragrances, it produces a particularly clear, green overall impression.