山毛榉科（Fagaceae）亦称壳斗科，属双子叶植物纲。本科植物除热带非洲及南非地区不产外，在北半球均有分布，并以亚洲种类最多。

本科的植物都是落叶或常绿乔木，单叶互生，全缘或有齿缺或羽状分裂；花雌雄同株，雄花是柔荑花序或头状花序，花被4-8裂，雄蕊4-20枚，雌花单生或簇生，花被4-8裂，子房下位；果实为具一粒种子的坚果，这种坚果特称为「槲果」。种子包藏在「壳斗」内，壳斗外生有尖刺或鳞片，有的壳斗形成一个杯子形的壳半包着坚果。

The family Fagaceae includes beeches and oaks, and comprises about 1200 species of both evergreen and deciduous trees and shrubs, which are characterized by alternate simple leaves with pinnate venation, unisexual flowers in the form of catkins, and fruit in the form of cup-like (cupule) nuts. Fagaceous leaves are often lobed and both petioles and stipules are generally present. Fruits lack endosperm and lie in a scaly or spiny husk that may or may not enclose the entire nut, which may consist of one to seven seeds. The best-known group of this family is the oaks, genus Quercus, the fruit of which is a non-valved nut (usually containing one seed) called an acorn. The husk of the acorn in most oaks only forms a cup in which the nut sits. Fagaceae are one of the most ecologically important woody plant families in the Northern Hemisphere, as oaks form the backbone of temperate forests in North America, Europe, and Asia and one of the most significant sources of wildlife fodder.