Fagus mexicana, the Mexican Beech or Haya, is a species of beech endemic to northeastern and central Mexico, where it occurs from southwest Tamaulipas south to Hidalgo and Puebla. It is restricted to high altitude cloud forests in mountains.
It is closely related to the American Beech Fagus grandifolia, and is treated as a subspecies of it by some (particularly U.S.) authors (as Fagus grandifolia subsp. mexicana (Martínez) E. Murray); however, Mexican literature generally treats it as a distinct species.
Fagus mexicana is a deciduous tree, reaching heights of 25–40 m tall and up to 1 m trunk diameter. The leaves are alternate, simple, with a slightly toothed margin, usually smaller than those of American Beech, 5–8 cm long and 3–5 cm broad. The buds are long and slender, 15–25 mm long and 2–3 mm thick.
The flowers are small catkins which appear shortly after the leaves in spring. The seeds are small triangular nuts 15–20 mm long and 7–10 mm wide at the base; there are two nuts in each cupule, maturing in the autumn 6–7 months after pollination.