Gonystylus eximius grows as a small tree up to 5 metres (20 ft) tall, with a stem diameter of up to 10 centimetres (4 in). Twigs are yellowish brown. Its flowers are reddish brown. The specific epithet eximius is from the Latin meaning "excellent". Habitat is lowland mixed dipterocarp forest from sea-level to 250 metres (800 ft) altitude. G. eximius is endemic to Borneo where it is known only from Sarawak.