Ol Donyo Sabuk National Park, Nature reserve in Central Province, Kenya

Ol Donyo Sabuk is a national park of 20.7 km2 whose highest point is the mountain of the same name, rising to 2,145 m from flat surroundings. The forested slopes hold about 250 buffalo, along with colobus monkeys, baboons, bushbuck, impala, duiker and abundant birdlife. The steep ascent requires a 4WD vehicle.

William Northrup McMillan, an American philanthropist, was the first non-native settler here. In 1905 he took a 99-year lease on 4,000 ha north of Nairobi, creating Juja Farm with its electrically lit Juja House. The national park was established in 1967. Near the summit lie the graves of McMillan (1872–1925), his wife Lady Lucie and their dog.

The Maasai name Ol Donyo Sabuk means "large mountain"; the Kamba call it Kyanzavi, after the nzavi or lablab bean. Kikuyu traditionalists know it as Kea-Njahe, the "Mountain of the Big Rain", one of Ngai's lesser homes. The name Kilimambogo combines Swahili kilima (hill) and mbogo (buffalo), after the herds on its forested slopes.

The journey from Nairobi takes roughly one hour by vehicle and is possible year-round. The best months for spotting wildlife are June through September and January through February.

The summit holds the graves of Sir William Northrup McMillan (1872–1925), his wife Lady Lucie and their dog, plus a separate grave of Louise, who joined the household at 13 and stayed until her death. The park was gazetted in 1967 and covers 20.7 km².