千层树是生长在澳洲的一个植物属，目前已知有236种，其中230种原产于澳洲，其余生长在印度尼西亚、新几内亚、新喀里多尼亚和马来西亚，为桃金娘科植物。白千层属，又名千层树属。

千层树和红千层（Callistemon）亲缘关系较近，两者主要区别是千层树的雄蕊成束，红千层的雄蕊是分别独立的。

野生的千层树主要生长在靠近水边或沼泽地边缘。

千层树的种类很多，不容易区分，一般为了和红千层区分，都叫做“白千层”。也有小型的被成为“蜜桃金娘”，也有可以提炼香精油的种类，由于提炼出的油叫做“茶油”而被称为“油茶树”（Melaleuca alternifolia），有的灌木树叶当年被早年移居的欧洲人作为茶的代用品。千层树的树皮色泽较淡，但生长在水边的树有时被树叶的颜色侵透显成棕色。

Melaleuca /ˌmɛləˈljuːkə/ is a genus of nearly 300 species of plants in the myrtle family, Myrtaceae, commonly known as paperbarks, honey-myrtles or tea-trees (although the last name is also applied to species of Leptospermum). They range in size from small shrubs that rarely grow to more than 1 m (3 ft) high, to trees up to 35 m (100 ft). Their flowers generally occur in groups, forming a “head” or “spike” resembling a brush used for cleaning bottles, containing up to 80 individual flowers. They are superficially like Banksia species, which also have their flowers in a spike, but the structure of individual flowers in the two genera are very different.