Psidium guajava (common guava, lemon guava) is a small tree in the Myrtle family (Myrtaceae), native to Mexico, Central America, and northern South America. Although related species may also be called guavas, they belong to other species or genera, such as the "pineapple guava" Acca sellowiana.

Guavas originated from an area thought to extend from Mexico or Central America and were distributed throughout tropical America and Caribbean region.They were adopted as a crop in subtropical and tropical Asia, the southern United States (from Tennessee and North Carolina south, as well as the west and Hawaii), tropical Africa, South Asia, Southeast Asia, and Oceania. Guavas are now cultivated in many tropical and subtropical countries. Several species are grown commercially; apple guava and its cultivars are those most commonly traded internationally.

Mature trees of most species are fairly cold-hardy and can survive temperatures slightly colder than 25 °F for short periods of time, but younger plants will likely freeze to the ground.

Guavas were introduced to Florida in the 19th century

Guavas are of interest to home growers in subtropical areas as one of the few tropical fruits that can grow to fruiting size in pots indoors. When grown from seed, guavas bear fruit as soon as two years and as long as 40 years