Pinus merkusii is a medium-sized to large
tree, reaching tall and with a trunk diameter of up to . 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, long and less than thick, green to yellowish green. The
cones are narrow conic, long and 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 long, with a wing, and are wind-dispersed.
Related species Pinus merkusii is closely related to the
Tenasserim pine (
P. latteri), which occurs farther 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
P. latteri differs in longer () 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. ==Distribution==