Miconia is a genus of flowering plants in the glory bush family, Melastomataceae, native to warm temperate to tropical regions of the Americas. The species are mostly shrubs and small to medium-sized trees up to 15 m tall. The generic name honours Catalan physician and botanist Francesc Micó. Some species are known by the common name johnnyberry.

Many species are threatened by habitat destruction in their native range, and some are feared to be on the brink of extinction. On the other hand, M. calvescens is a contributing factor in the decline and maybe even extinction of other plants: it has become a highly invasive weed on a number of Pacific Islands where it was introduced, including Hawaii and Tahiti. It is often referred to as the "purple plague" or the "green cancer" in reference to its habit of overgrowing native ecosystems, and its leaves which are bright green above and bright purple below.

Miconia fruit are a favorite food of many birds (invasive M. calvescens spreads by this route). The leaves of some species are eaten by caterpillars of the moth-butterflies (Hedylidae).

As of 2023, genus Miconia comprises nearly 1,900 species, with new species occasionally being discovered. Among them are: