Rhodomyrtus tomentosa, commonly known as the Rose Myrtle or Downy Rose Myrtle, is a species of flowering plant from the family Myrtaceae. Rhodomyrtus tomentosa is native to Southeast Asia and can be found in countries including Thailand, Malaysia, Indonesia, and the Philippines. Moreover, Rhodomyrtus tomentosa is an evergreen shrub or small tree that grows up to 3–5 m in height with dark green, glossy leaves that are elliptical in shape and covered in fine, soft hairs. The flowers are usually solitary, white, and have a distinctive star-like shape, whereas dark purple to black berry-like fruit is edible in nature. Literature reported that Rhodomyrtus tomentosa is well adaptable to various habitats and can be found in both lowland and montane forests. Rhodomyrtus tomentosa contains numerous bioactive phytopharmaceuticals, including rhodomyrtone and its by-products, myricitrin, piceatannol, quercetin, dihydromyricetin, kaempferol, and vitexin. Additionally, antimicrobial assays demonstrated that the plant contains effective antimicrobial complexes with a diversity of mechanisms of action. This chapter provides updated information on the chemical conformation, pharmacology, and toxicology of the herb and its primary bioactive compounds.