ex de Vriese Gymnostoma sumatranum is a tree in the she-oak family, Casuarinaceae, native to Southeast Asia and the Malesia region.

According to Plants of the World Online, Gymnostoma sumatranum is endemic to the island of Sumatra in Indonesia.

[2] The IUCN Red List indicates a wider range for the species, including Sumatra, Java, Peninsular Malaysia, Borneo, the Philippines, Sulawesi, Maluku, New Guinea, the Bismark Archipelago, and the Solomon Islands.

Gymnostoma sumatranum is characterised by its multiple rounded umbrella-shaped crowns, while Casuarina equisetifolia (the most well-known member of Casuarinaceae) is typified by its equisetoid appearance.

Like the other members of the family Casuarinaceae, they are characterized by drooping equisetoid (meaning "to look like Equisetum") twigs, are evergreen, and monoecious or dioecious.