Melaleuca is a genus of plants in the myrtle family Myrtaceae known for its natural soothing and cleansing properties. There are well over 200 recognised species, most of which are endemic to Australia. A few species occur in Malesia and 7 species are endemic to New Caledonia.

The species are shrubs and trees growing (depending on species) to 2–30 m (6.6–98 ft) tall, often with flaky, exfoliating bark. The leaves are evergreen, alternately arranged, ovate to lanceolate, 1–25 cm (0.39–9.8 in) long and 0.5–7 cm (0.20–2.8 in) broad, with an entire margin, dark green to grey-green in colour.

The flowers are produced in dense clusters along the stems, each flower with fine small petals and a tight bundle of  stamens; flower colour varies from white to pink, red, pale yellow or greenish. The fruit is a small capsule containing numerous minute seeds.

Melaleuca is closely related to the genus Callistemon; the main difference between the two is that the stamens are generally free in Callistemon but grouped into bundles in Melaleuca. In the wild, Melaleuca plants are generally found in open forest, woodland or shrubland, particularly along watercourses and the edges of swamps.

The best-accepted common name for Melaleuca is simply melaleuca; however most of the larger species are also known as tea tree, and the smaller types as honey myrtles, while those species in which the bark is shed in flat, flexible sheets are referred to as paperbarks. The Tea tree is presumably named for the brown colouration of many water courses caused by leaves shed from trees of this and similar species (for a famous example see Brown Lake (Stradbroke Island)). The name "tea tree" is also used for a related genus, Leptospermum, also in Myrtaceae.

One well-known melaleuca, M. alternifolia, is notable for its essential oil which is both anti-fungal and antibiotic, while safely usable for topical applications. This is produced on a commercial scale and marketed as Tea Tree Oil. Australian Aborigines have used the leaves for many medicinal purposes, including chewing the young leaves to alleviate headache and for other ailments.

Scientific studies have shown that tea tree oil made from M. alternifolia is a highly effective topical antibacterial and antifungal, although it may be toxic when ingested internally in large doses or by children. In rare cases, topical products can be absorbed by the skin and result in toxicity. The oils of Melaleuca can be found in organic solutions of medication that claims to eliminate warts, including the Human papillomavirus. No scientific evidence proves this claim. Melaleuca oils are the active ingredient in Burn-Aid, a popular minor burn first aid treatment (an offshoot of the brandname Band-Aid).

M. leucadendra oil, cajeput tree, is also used in many pet fish remedies such as Melafix and Bettafix to treat bacterial and fungal infections. Bettafix is a lighter dilution of cajeput tree oil, while Melafix is a stronger dilution. It is most commonly used to promote fin and tissue regrowth. The remedies are often associated with Betta fish (Siamese Fighting Fish) but are also used with other fish.

Melaleuca bark is used to make a natural bio-degradable paper or papyrus which is considered by many to be a renewable resource and therefore much more environmentally friendly than modern paper farming or deforestation.