Dipterocarpus retusus, commonly known as hollong, is a large tree and perhaps the best known species in the genus Dipterocarpus. It is native to China, Vietnam, Philippines, Laos, Cambodia, Malaysia, Indonesia, Myanmar, and India. The tree, some 20–30 metres (70–100 ft) tall, is found in Cambodia in dense forests of the plains, common on hillsides and along rivers and in forests between 800 m (2,600 ft) and 1,500 m (5,000 ft) altitude.

Hollong is the state tree of Assam and Arunachal Pradesh, India. In India, the timber is used for plywood and making various containers. In China, the timber is used in construction. Hollong is a sacred tree for Moran community of Assam.

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