Tangkoko Batuangus Nature Reserve, Nature reserve with mountains and rainforest in northern Sulawesi, Indonesia.

Tangkoko Batuangus Nature Reserve covers 8,718 hectares in northern Sulawesi and includes Mount Tangkoko (1,109 m), Mount Dua Saudara (1,361 m) and Mount Batuangus (450 m). Its terrain runs from coastal forest and lowland rainforest to mossy montane forest, with two ecosystems: rainforest and cloud forest. Lowland trees include Palaquium species, Cananga odorata and Dracontomelon dao.

Mount Tangkoko was first protected by the Dutch East Indies government in 1919 under Decree GB 21/2/1919 (Stbl. 90). The Duasudara area of 4,299 hectares was added in 1978, and on 24 December 1981 a ministerial decree created the Tangkoko Batuangus Nature Reserve, together with the Batuputih and Batuangus tourism parks. Visitation is permitted only in the Batuputih area.

The reserve is named after its two peaks, Tangkoko and Batuangus, and the Indonesian name adds Dua Saudara, the third summit. Visitors enter only through Batuputih, where guides from the surrounding villages lead night walks to see tarsiers. A 2005 survey of three nearby villages found that residents still hunted macaques and cuscus for meat and for sale, so conservation work here runs alongside local livelihoods.

Wear sturdy shoes, bring insect repellent, and prepare for hot and humid tropical conditions when exploring the terrain. Starting early in the day and carrying plenty of water is advisable, as hiking the steep slopes requires physical effort.

Alfred Russel Wallace collected babirusa and maleo specimens at Tangkoko in 1861, when maleo still nested in the black sand of the beach. That colony was gone by 1915. Between 1978 and 1993 hunting cut crested macaques by 75%, maleo by 90% and bear cuscus by 95%.