The waterbuck is a large antelope found widely in sub-Saharan Africa. It is placed in the genus Kobus of the family Bovidae. It was first described by Irish naturalist William Ogilby in 1833. Its 13 subspecies are grouped under two varieties: the common or ellipsiprymnus waterbuck and the defassa waterbuck. The head-and-body length is typically between 177 and 235 cm and the typical height is between 120 and 136 cm. In this sexually dimorphic antelope, males are taller and heavier than females. Males reach roughly 127 cm (50 in) at the shoulder, while females reach 119 cm (47 in). Males typically weigh 198–262 kg (437–578 lb) and females 161–214 kg (355–472 lb). Their coat colour varies from brown to grey. The long, spiral horns, present only on males, curve backward, then forward, and are 55–99 cm (22–39 in) long.

Nairobi National Park is a national park in Kenya that was established in 1946 about 7 km (4.3 mi) south of Nairobi. It is fenced on three sides, whereas the open southern boundary allows migrating wildlife to move between the park and the adjacent Kitengela plains. Herbivores gather in the park during the dry season. Nairobi National Park is negatively affected by increasing human and livestock populations, changing land use and poaching of wildlife. Despite its proximity to the city and its relative small size, it boasts a large and varied wildlife population, and is one of Kenya's most successful rhinoceros sanctuaries.