There are two species of lechwes: the common lechwe (Kobus leche) and the Nile lechwe (K. megaceros). The three subspecies of the common lechwe—the red lechwe (K. leche leche), the Kafue lechwe (K. leche kafuensis), and the black lechwe (K. leche smithemani)—inhabit floodplains bordering marshes and swamps of the southern savanna, from southeastern Congo (Kinshasa) through Zambia and northern Botswana to Angola. The Nile lechwe lives on the Nile floodplain bordering Al-Sudd (Sudd, Al-) swamp in southern Sudan.

Lechwes are sizeable, long-horned (males only) antelopes with a sturdy build. Hindquarters are higher and more massive than forequarters, the neck is long, and the muzzle is short and rather blunt. Lechwes are unusual in having widely splayed, elongated hooves that support them on soft ground (e.g., sitatunga). Their shoulder height is 85–105 cm (33–41 inches), and their weight is 60–130 kg (130–290 pounds); males are 20 percent larger than females. Their lyre-shaped, heavily ridged horns are 45–90 cm (18–35 inches) long.

The coat is greasy and water-repellent. Females have tawny to chestnut coats and look much alike, apart from minor differences in markings. Red lechwe females are the most colourful; they are bright chestnut with white underparts, throat patch, facial markings, and undertail and with black stripes down the front of their legs. The presence of mature males is advertised not only by the sweeping long horns and head-high proud posture but by darker coats and markings, which are most pronounced in the black lechwe of Zambia's Lake Bangweulu. However, the most extreme contrast is seen in Nile lechwe rams, which are dark chocolate brown with whitish markings that include a large patch on the neck and shoulders.

Concentrations of up to 1,000 lechwes per square kilometre are not uncommon late in the dry season on shrinking greenbelts. Females and young stay closest to the water, upon which lechwes, clumsy runners on dry land, depend to escape predators. Bachelor males aggregate on drier ground farther from the water and are kept separate by the aggression of territorial males, some of which also occupy sizeable properties farther inland, where females come during the rains when the population is more dispersed. However, most males become territorial only during the annual mating peak, which occurs when lechwes are most concentrated (December to January in Zambia, early in the rains). This is when lekking occurs, typically in a roughly circular arena about 0.5 km (0.3 mile) across where 50–100 males display to approaching females—most of which come to the leks to mate, but with just a few centrally placed males. Because aggregations are continually on the move, the leks are only temporary.