The Sumatran Pine (Pinus merkusii) is a pine native to southeast Asia, mainly in the mountains of northern Sumatra, and with two outlying populations, on Gunung (Mt.) Kerinci and Gunung Talang in central Sumatra, and in the Philippines on Mindoro and the Zambales Mountains of western Luzon. The population in central Sumatra, between 1° 40' and 2° 06' S latitude, is the only natural occurrence of any pine south of the Equator. It generally occurs at moderate altitudes, mostly from 400-1500 m, but occasionally as low as 90 m and up to 2000 m.

It is a medium-sized to large tree, reaching 25-45 m tall and with a trunk diameter of up to 1 m. The bark is orange-red, thick and deeply fissured at the base of the trunk, and thin and flaky in the upper crown. The leaves ('needles') are in pairs, very slender, 15-20 cm long and less than 1 mm thick, green to yellowish green. The cones are narrow conic, 5-8 cm long and 2 cm broad at the base when closed, green at first, ripening glossy red-brown. They open to 4-5 cm broad at maturity to release the seeds. The seeds are 5-6 mm long, with a 15-20 mm wing, and are wind-dispersed.

Sumatran Pine is closely related to Tenasserim Pine Pinus latteri, which occurs further north in southeast Asia from Myanmar to Vietnam; some botanists treat the two as conspecific (under the name P. merkusii, which was described first), but the Tenasserim Pine differs in longer (18-27 cm) and stouter (over 1 mm thick) leaves and larger cones with thicker scales, the cones often remaining closed for some time after maturity. It is also related to the group of Mediterranean pines including Aleppo Pine and Turkish Pine, which share many features with it.