The black giant squirrel or Malayan giant squirrel (Ratufa bicolor) is a large tree squirrel in the genus Ratufa native to the Indomalayan zootope. It is found in forests from northern Bangladesh, northeast India, eastern Nepal, Bhutan, southern China, Myanmar, Laos, Thailand, Malaysia, Cambodia, Vietnam, and western Indonesia (Java, Sumatra, Bali and nearby small islands).
The black giant squirrel is one of the largest species of squirrel in the world. On average, an adult black giant squirrel weighs around 1.05–1.25 kg (2.3–2.8 lb), has a head–and–body length of 34–37 cm (13–15 in), and the tail is 41–42 cm (16–17 in) long. The subspecies R. b. condorensis of Vietnam's Côn Sơn Island averages only c. 30 cm (12 in) in head–and–body length and the tail 32 cm (13 in), but otherwise it resembles the typical subspecies.
This species is typically distinctly bicoloured with dark upperparts and pale underparts. The back, top of the head, ears and bushy tail are deep brown to black and the underparts are light buff-coloured. In Sumatra, Java and Bali the hairs of the back and tail are light-tipped, making these sections appear relatively pale (however, the back is still distinctly darker than the underparts). On small islands off Myanmar and in the Strait of Malacca the black giant squirrel has reddish-yellowish underparts.
Ratufa bicolor's range includes a variety of bioregions that all share the commonality of being forested. It ranges in elevation from sea level up to at least 1,400 metres (4,600 ft), in some of the most rugged land in the world. However, in recent decades, R. bicolor's habitat has been steadily encroached upon by human settlement, timber harvesting and agriculture, which along with overhunting by human predation in parts of its range, has resulted in a total loss of up to 30% of the population in the past ten years. However, in some places this species is protected from hunting by law or tradition.