Most Venomous Spiders in the World: Facts and Real Risks

Are all spiders venomous?

Almost every spider has venom glands and uses venom to paralyze insects and other small prey. Only a few families, such as the cribellate orb weavers (Uloboridae), have lost their venom glands and wrap their prey in silk instead. For nearly all species, though, the fangs are too small to pierce human skin or the venom is too weak to matter. Our guide Are all spiders venomous? explains why venom and danger are not the same thing.

The spiders below are ranked by how serious their bites can be for people, combining venom strength with medical records. Deaths are rare for every one of them today.

1. Sydney funnel-web spider: dangerous to primates

The Sydney funnel-web (Atrax robustus) is a glossy black spider with a body about 2–4 cm (0.8–1.6 in) long that lives in burrows in and around Sydney, Australia. In the warmer months, males leave their burrows to search for females and sometimes wander into gardens, garages and shoes, or fall into swimming pools, where they can survive for hours by trapping air bubbles. Males are the dangerous sex: there are no records of severe bites from females.

The venom contains delta-atracotoxin, which attacks the nervous system of people and other primates but has little effect on many other mammals. The Sydney funnel-web group has caused 13 documented deaths, seven of them children. Since an antivenom became available in 1981, no one has died from a funnel-web bite. Making the antivenom is laborious: one dose needs about 70 venom milkings, so Australians are sometimes asked to hand in live spiders.

In 2025, scientists split the Sydney funnel-web into three species, including the large Newcastle funnel-web (Atrax christenseni), which responds to the same antivenom. The northern tree-dwelling funnel-web of Queensland and northern New South Wales is also considered potentially deadly.

2. Brazilian wandering spiders: the “armed spiders”

Brazilian wandering spiders (genus Phoneutria) are large, fast hunters with a leg span of 13–18 cm (5–7 in). They live in forests from Costa Rica to northern Argentina and roam the forest floor at night instead of building webs. When threatened, they rear up and raise their front legs, which earned them the Brazilian name armadeiras, or “armed spiders.” By day they hide in termite mounds, bromeliads and banana plants, hence the nickname “banana spider.”

Their neurotoxic venom can cause intense pain, sweating, a racing heart and, in men, painful erections, and a few well-documented deaths have occurred, mostly in young children. Most bites are far milder: studies in Brazil suggest the spiders inject venom in only about a third of bites, and only about 2% of cases need antivenom. Reports of wandering spiders arriving in banana shipments to Europe and North America are often exaggerated, since most of these “banana spiders” turn out to be harmless species.

3. Widow spiders: black widows and redbacks

Widow spiders (genus Latrodectus) live on every continent except Antarctica. They include the black widows of North America, the redback of Australia and the Mediterranean black widow of southern Europe and Central Asia. Only females, with bodies up to about 1.3 cm (0.5 in) long, are large enough to harm people. Their venom contains alpha-latrotoxin, which floods nerves with chemical signals and can cause severe pain, muscle cramps, sweating and a racing heart, a condition called latrodectism.

Despite their reputation, widow bites are rarely fatal. A 2012 review of US poison center data found no deaths from black widow bites since 1983, and in Australia no deaths have been directly caused by redbacks since an antivenom was introduced in 1956. Widow spiders are shy and usually bite only when pressed against skin. Learn more on our southern black widow page.

4. Recluse spiders: brown and Chilean recluses

Recluse spiders (genus Loxosceles) have six eyes arranged in three pairs, while most spiders have eight. Their venom contains an enzyme called sphingomyelinase D, which can destroy skin and tissue around a bite. The brown recluse (Loxosceles reclusa) lives in the central and southern United States, roughly from Nebraska and Ohio south to Texas and Georgia. Despite rumors, it is not established in California or elsewhere in the West.

Most brown recluse bites are minor. A minority cause a slowly healing wound, and rarely, mainly in young children, the venom causes serious illness throughout the body. The Chilean recluse (Loxosceles laeta) of South America is considered the most dangerous recluse: in a study of bites in Santiago, Chile, about one case in five involved serious illness beyond the skin. The Mediterranean recluse (Loxosceles rufescens) lives in southern Europe and has spread to many other countries.

5. Six-eyed sand spiders: potent but almost never met

Hahn’s six-eyed sand spider (Hexophthalma hahni) lives in deserts and sandy scrublands of Namibia, Zimbabwe and South Africa. A relative of the recluses, it hides beneath stones or buried in sand, waiting for prey, with velvety hairs that hold sand grains as camouflage. Laboratory studies show its venom is a powerful tissue-destroying mix, and it is often listed among the most venomous spiders. Yet there are no proven bites to people in southern Africa, because the spider is secretive and lives far from towns.

Painful but rarely dangerous: false widows and others

Many spiders blamed for “dangerous bites” are much less harmful. The noble false widow (Steatoda nobilis), originally from Madeira and the Canary Islands, is now common in buildings across Britain and Ireland. Its bite usually causes symptoms like a bee or wasp sting, although some people need treatment for infections. The hobo spider has been blamed for skin wounds in the northwestern United States, but actual bites have not been shown to cause such damage. Read Are house spiders dangerous? for the spiders most people meet at home.

Most venomous spiders at a glance

How dangerous are spiders really?

Spiders are among the most feared animals, but they rarely seriously hurt anyone. In Australia, home of the funnel-webs and redbacks, a study of 750 bites by identified spiders found that only about 6% caused significant effects. Many “spider bites” are not spider bites at all: a 2016 review found that most published case reports of supposed bites could not be verified, and skin infections such as MRSA are often mistaken for recluse bites. In Britain, bee and wasp stings cause far more deaths than spiders.

Venomous spiders across North America are covered in our guide to venomous spiders in the US, and other record-breaking venoms are in our list of the most venomous animals.

How to avoid spider bites

Most bites happen when a spider is trapped against skin. In areas with funnel-webs or widows, shake out shoes, gloves and clothing left outdoors, wear gloves when gardening or moving wood and rubble, and never handle a spider you cannot identify. If you are bitten by a spider that might be dangerous, or develop symptoms such as spreading pain, sweating or difficulty breathing, seek emergency medical help immediately: call 911 in the US, 112 in the EU or 999 in the UK.