An elytron (//; from Greek ἔλυτρον "sheath, cover"; plural: elytra /-/) is a modified, hardened forewing of certain insect orders, notably beetles (Coleoptera) and a few of the true bugs (Hemiptera) such as the family Schizopteridae; in most true bugs, the forewings are instead called hemelytra (sometimes alternatively spelled as "hemielytra"), as only the basal half is thickened while the apex is membranous. An elytron is sometimes also referred to as a shard.
The elytra primarily serve as protective wing-cases for the hindwings underneath, which are used for flying. To fly, a beetle typically opens the elytra and then extends the hindwings, flying while still holding the elytra open, though some beetles in the families Scarabaeidae and Buprestidae can fly with the elytra closed.
In a number of groups, the elytra are reduced to various degrees, (e.g., the beetle family Ripiphoridae), or secondarily lost altogether, as in various Elateroidea lineages with wingless females.
In some flightless groups, the elytra are present but fused together, and the hindwings are absent. Some of the ground beetles (family Carabidae) are a good example of this.