Catharanthus roseus, commonly known as bright eyes, Cape periwinkle, graveyard plant, Madagascar periwinkle, old maid, pink periwinkle, rose periwinkle, is a perennial species of flowering plant in the family Apocynaceae. It is native and endemic to Madagascar, but is grown elsewhere as an ornamental and medicinal plant, and now has a pantropical distribution. It is a source of the drugs vincristine and vinblastine, used to treat cancer. It was formerly included in the genus Vinca as Vinca rosea.

It has many vernacular names among which are arivotaombelona or rivotambelona, tonga, tongatse or trongatse, tsimatiririnina, and vonenina.

Two varieties are recognized

Following the Jurassic period approximately 185 million years ago, the supercontinent Gondwana separated into two distinct geographic areas: east Gondwana (Madagascar, Antarctica, Australia and the Indian subcontinent) and west Gondwana (Africa, South America), leading to the geographic location of the island of Madagascar. It is now known as one of the fourth largest islands in the world, developing its own extraordinary biodiversity in isolation. This has led to unique species and a diverse array of approximately 15000 plants and over 10000 angiosperm species, 84% being endemic to Madagascar. It was within this ecosystem that the periwinkle came to existence.

The presence of over 200 alkaloids within the plant, including vinblastine and vincristine and their use in cancer drugs, are a result of the plant's response to environmental threats and pressures. Studies have shown that compounds isolated from C. roseus are examples of secondary metabolites, which have contributed to the plant's ability to defend itself against herbivores and other pathogens, allowing it an advantage from predators or other pathogens within their immediate environment. These secondary metabolites would contrast from primary metabolites used for growth and development. Studies have shown that biosynthetic pathways, such as catharanthine and vindoline, accumulate separately in the plant, allowing for it to evade common pests such as Egyptian Cotton leafworm, Spodoptera littoralis.

Within single cell genome analysis, gene clusters within C. roseus have been identified through MIA biosynthesis, including the Vinca alkaloids. Within plants, the genome evolved through different forms of gene duplication, which involved either whole chromosomes, segmental duplications, tandem or dispersed duplications. Millions of years of evolution led to the encoding of the enzymes for the complex biosynthetic pathways we see in C. roseus, which further accounts for the many compounds synthesized, as well as recent studies highlighting the role of random spontaneous mutations further influencing a plant's genetic information.

Catharanthus roseus is an evergreen subshrub or herbaceous plant growing 1 m (39 in) tall. The leaves are oval to oblong, 2.5–9 cm (1.0–3.5 in) long and 1–3.5 cm (0.4–1.4 in) wide, glossy green, hairless, with a pale midrib and a short petiole 1–1.8 cm (0.4–0.7 in) long; they are arranged in opposite pairs. The flowers range from white with a yellow or red center to dark pink with a darker red center, with a basal tube 2.5–3 cm (1.0–1.2 in) long and a corolla 2–5 cm (0.8–2.0 in) diameter with five petal-like lobes. The fruit is a pair of follicles 2–4 cm (0.8–1.6 in) long and 3 mm (0.1 in) wide.

In its natural range along the dry coasts of southern Madagascar, Catharanthus roseus is considered weedy and invasive, often self-seeding prolifically in disturbed areas along roadsides and in fallow fields. It is also widely cultivated and is naturalized in subtropical and tropical areas of the world such as Australia, Bangladesh, India, Malaysia, Pakistan, and the United States. It is so well adapted to growth in Australia that it is listed as a noxious weed in Western Australia and the Australian Capital Territory, and also in parts of eastern Queensland.