Lablab purpureus is a species of bean in the family Fabaceae. It is native to sub-Saharan Africa and it is cultivated throughout the tropics for food. English language common names include hyacinth bean, lablab-bean bonavist bean/pea, dolichos bean, seim or sem bean, lablab bean, Egyptian kidney bean, Indian bean, bataw and Australian pea. Lablab is a monotypic genus.

The name lablab which is also capitalized as its genus name is given by Robert Sweet from the previous name of Dolichos lablab by Carl Linnaeus, its epithet comes from Arabic: لَبْلَاب, romanized: lablāb.

According to the British biologist and taxonomist Bernard Verdcourt,

The plant is variable due to extensive breeding in cultivation, but in general, they are annual or short-lived perennial vines. The wild species is perennial. The thick stems can reach 6 m (20 ft) in length. The leaves are made up of three pointed leaflets, each up to 15 cm (5.9 in) long. They may be hairy on the undersides. The inflorescence is made up of racemes of many flowers. Some cultivars have white flowers, and others may have purplish or blue.

The fruit is a legume pod variable in shape, size, and color. It is usually several centimeters long and bright purple to pale green. It contains up to four seeds. Depending on the cultivar, the seeds are white, brown, red, or black, sometimes with a white hilum. Wild plants have mottled seeds. The seed is about a centimeter long.

The exact origin of the lablab bean remains uncertain. Evidence of wild varieties in eastern and southern Africa suggests these regions as the likely source, although some theories suggest India as the origin.

Over the centuries, the lablab has been distributed all over the world. Despite its preference for tropical and subtropical climates, it can be found in temperate climates such as Central and South America or Italy. Its adaptability to different climates increases its agricultural value.

The lablab bean remains most widespread in tropical and subtropical areas, particularly in eastern and southern Africa and India. There, the legume is grown primarily for food and fodder, but its cultivation has declined sharply in many regions of Africa, despite renewed interest in its soil-improving functions in multiple cropping systems. One of the main reasons for this decline is the replacement of faba bean by the common bean, but factors such as the many processing steps and antinutritional factors may also have played a role. In addition, lablab is often grown in home garden systems or mixed cropping systems, such as in Southeast Asia, making estimates of global production difficult.