Carpinus betulus - European Hornbeam
Carpinus caroliniana - American Hornbeam
Carpinus cordata - Sawa Hornbeam
Carpinus fargesii - Farges' Hornbeam
Carpinus laxiflora - Aka-shide Hornbeam
Carpinus japonica - Japanese Hornbeam
Carpinus orientalis - Oriental Hornbeam
Carpinus tschonoskii - Chonowski's Hornbeam
Carpinus turczaninowii - Turkzaninov's Hornbeam

The hornbeams (Carpinus) are a genus of relatively small hardwood trees, placed in the birch family Betulaceae, though some botanists separate it off together with the hazels (Corylus) and hop-hornbeams (Ostrya) into a segregate family Corylaceae. The 30-40 species occur across much of the north temperate regions, with the greatest number of species in east Asia, particularly China. Only two species occur in Europe, and only one in eastern North America.

The leaves are deciduous, alternate, and simple with a serrated margin, and typically vary from 3-10 cm in length. The flowers are wind-pollinated pendulous catkins, produced in spring. The male and female flowers are on separate catkins, but on the same tree (monoecious). The fruit is a small nut about 3-6 mm long, held in a leafy bract; the bract may be either trilobed or simple oval. There are typically 10-30 seeds on each seed catkin.

The European Hornbeam (Carpinus betulus), is a small to medium sized tree, typically 10-20 m tall but occasionally reaching 30 m. It is native to most of Europe except for northern Britain and most of Scandinavia. The leaves are 5-9 cm long, and the seeds have a 3-4 cm long trilobed bract.

The Oriental Hornbeam (Carpinus orientalis) occurs in southeast Europe and southwest Asia, usually on hot dry sites at lower altitudes than C. betulus, and is a smaller tree, rarely over 10 m tall and often shrubby. It has small leaves, 3-5 cm long. The seeds differ from C. betulus in having a simple bract (not trilobed), about 2 cm long.

The Japanese Hornbeam (Carpinus japonica) is similar to C. orientalis in having unlobed seed bracts, but differs from it in having larger leaves, 8-10 cm long.

The North American species, American Hornbeam (Carpinus caroliniana) is similar to C. betulus in leaf size and shape. The seed bract is also trilobed, but less deeply than in C. betulus.

The wood of hornbeams is very hard, and not used much due to the difficulty of working it. Its hardness has however lent it to use for carving boards, tool handles, coach wheels and other situations where a very tough, hard wood is required.

The common English name of "hornbeam" derives from the hardness of the wood (likened to horn) and the Old English beam, a tree (cognate with German "baum"). American Hornbeam is also occasionally known as blue-beech, ironwood, or musclewood; the first from the resemblance of the bark to that of the American Beech Fagus grandifolia, the other two from the hardness of the wood and the muscular appearance of the trunk respectively.