Spiders are carnivorous arthropods that coexist with humans and ambush or ensnare prey. Unlike other arthropods, spiders rarely transmit communicable diseases, and play a critical role in the ecosystem by consuming other arthropods that frequently transmit human diseases, such as mosquitoes and flies. There are more than 30,000 species of spiders, most of which are venomous, but they cannot inflict serious bites due to delicate mouthparts and short fangs. The differential diagnosis of spider bites is extensive and includes other arthropod bites, skin infections, and exposure to chemical or physical agents. However, approximately 200 species from 20 genera of spiders worldwide can cause severe human envenomings, with dermonecrosis, systemic toxicity, and death. Spider bites can usually be prevented by simple personal and domestic measures. Early species identification and specific management may help prevent serious sequelae of spider bites.