Orb weaver, any spider of the family Araneidae (Argiopidae or Epeiridae) of the order Araneida, a large and widely distributed group noted for their orb-shaped webs. More than 2,840 species in some 167 genera are known.
Notable among them are the garden spiders (subfamily Argiopinae), which are common in grassy areas and are brightly coloured—yellow and black or red and black. The oldest known orb weaver, Mesozygiella dunlopi, was described in 2006 from fossils discovered in Álava, Spain. The species was dated to the Early Cretaceous Epoch (about 145.5 million to 99.6 million years ago).
Some species of large orb weavers, including Argiope savignyi and certain members of the genera Araneus, Eriophora, and Parawixia, are suspected to prey on bats, particularly vesper bats (family Vespertilionidae) and sheath-tailed bats (family Emballonuridae).