Ostrya is a genus of eight to ten small deciduous trees belonging to the birch family Betulaceae. Its common name is Hophornbeam in American English and Hop-hornbeam in British English. It may also be called ironwood, a name shared with a number of other plants.
The genus is native in southern Europe, southwest and eastern Asia, and North and Central America. They have a conical or irregular crown and a scaly, rough bark. They have alternate and double-toothed birch-like leaves 3-10 cm long. The flowers are produced in spring, with male catkins 5-10 cm long and female catkins 2-5 cm long. The fruit form in pendulous clusters 3-8 cm long with 6-20 seeds; each seed is a small nut 2-4 mm long, fully enclosed in a bladder-like involucre.
The wood is very hard and heavy; the name Ostrya is derived from the Greek word 'ostrua', "bone-like", referring to the very hard wood. Regarded as a weed tree by some foresters, this hard and stable wood was historically used to fashion plane soles.