Hopea fluvialis is a tree in the family Dipterocarpaceae, native to Borneo. The specific epithet fluvialis means "of rivers", referring to species' habitat.
Hopea fluvialis grows up to 25m (82feet) tall, with a trunk diameter of up to 80cm (30inches). It may also have buttresses and stilt roots. The bark is smooth. The leaves are lanceolate to ovate and measure up to 12cm (05inches) long. The inflorescences measure up to 6cm (02inches) long and bear up to seven cream flowers. The nuts are egg-shaped and measure up to 1.1cm (00.4inches) long.
Hopea fluvialis is endemic to Borneo. Its habitat is lowland dipterocarp forests by rivers, to elevations of 970m (3,180feet).
Hopea fluvialis has been assessed as near threatened on the IUCN Red List. It is threatened by land conversion for tree plantations and agriculture and by logging for its timber. In Sarawak, fires are also a threat. The species is found in two protected areas in Sarawak.