The Sumatran Whistling-thrush (Myophonus castaneus) is a passerine bird belonging to the whistling-thrush genus Myophonus in the thrush family Turdidae. It is endemic to the island of Sumatra in Indonesia. In the past, it has often been lumped together with the Javan Whistling-thrush (M. glaucinus) and Bornean Whistling-thrush (M. borneensis) as the "Sunda Whistling-thrush" (M. glaucinus) but it is now often regarded as a separate species based on differences in plumage and measurements. It is also known as the Chestnut-winged Whistling-thrush or Brown-winged Whistling-thrush.
It is about 25 centimetres long. The black bill has an average depth of 7.3 millimetres, slenderer than the bills of the Bornean and Javan Whistling-thrushes. The legs and feet are dark brown. The adult male has a dark blue head, breast and shoulders with the rest of the plumage being chestnut. The adult female and immature are mostly dull chestnut-brown with a blue patch on the shoulder. The Bornean and Javan Whistling-thrushes lack any chestnut coloration.
It has a loud whistling call and a harsh grating call.
It occurs in montane forest from 400 to 1500 metres above sea-level. It is usually found near streams and typically keeps to the middle and subcanopy layers of the forest. It is a scarce bird and is believed to be declining as a result of deforestation.