The World’s Top 10 Most Venomous Spiders

The most dangerous spiders in the world possess powerful cytotoxic and neurotoxic venom. Deadly arachnids can deliver a painful bite with symptoms including necrosis, nausea, and respiratory failure.

Jul 15, 2023By Lisa Szymanski
most venomous spiders

Despite their small size, spiders are among the most feared creatures in the world. There are numerous species of spiders that are harmful to humans with some causing painful bites and others with potent venom affecting the nervous system. However, the availability of antivenin and the small size of these arachnids make fatalities by spider bites less likely. From their appearance to the effects of their venom, the following guide explores the world’s top 10 most venomous spiders and where to find them.

1. Brown Recluse Spider

brown recluse spider
The six-eyed brown recluse spider

The brown recluse spider is the most poisonous spider that is found in the United States. This dangerous arachnid possesses necrotic venom, and a single bite may cause severe tissue damage. These spiders have a light brown abdomen with darker legs. Their body length is 0.5 inches, and they have a distinct violin-shaped marking on the top of their head and thorax. To be sure that a spider is a brown recluse it must have six eyes and not the typical eight eyes other spiders have.

2. Wolf Spider

wolf spider in grass
A wolf spider ready to pounce

The wolf spider is similar in appearance to a tarantula possessing a broad and hairy body with long legs. These large-eyed spiders are called wolf spiders because they hunt by running after and pouncing on their prey. These venomous arachnids are found in North America, Europe, and even North of the Arctic. Wolf spiders reach a length of only 1 inch and like to hide in leaf matter or under logs and rocks. Although they are classified as poisonous arachnids, the bite of a wolf spider is comparable to a bee sting and causes itching, pain, and inflammation.

3. Australian Funnel Spider

funnel spider in defense
The Sydney funnel spider in defense

There are 40 species of funnel spiders ranging in size from 0.4 inches to just over 2 inches in body length. Their name is attributed to their funnel-shaped web that is used to trap prey. The most dangerous of this spider family is the Sydney funnel spider (Atrax robustus) which is responsible for the most fatalities by a spider bite. The venom of these arachnids contains atraxotoxin proteins that cause elevated heart rate, hypertension, and difficulty breathing in only 15 minutes in adults. However, with the development of antivenom in 1981, no fatalities have been recorded since.

4. Black Widow Spider

black widow spider web
Black widow spider releasing a web

A venomous arachnid that terrifies many is the black widow spider. Latrodectus mactans are identified by the unique red hourglass that is located underneath the abdomen. These highly poisonous spiders are found on every continent except for Antarctica. Female black widows can reach 2 inches in length, while males are 1 inch or smaller. The family of widow spiders has a neurotoxic venom that causes muscle and joint pain, nausea, headaches, and hypertension. Its bite is not fatal to healthy adults, but children and seniors are at higher risk of complications.

5. Yellow Sac Spider

yellow sac spider on green leaf
Yellow sac spider waits for prey

The yellow sac spider is a tiny arachnid reaching only 0.6 inches but packs a nasty bite. Belonging to the Clubionidae family of spiders, they are found in the United States and throughout South America. Yellow Sac Spiders have cytotoxic venom that leads to tissue damage. Bites cause inflammation, swelling, and possible necrosis, although this tends to heal quickly and is not as severe as the bite of the Brown Recluse.

6. Redback Spider

redback spider fangs
The redback spider has a large red stripe on its back

The redback spider is related to the black widow and is a highly poisonous arachnid. These poisonous arachnids are found in Australia, with sightings in New Zealand and Japan. Reaching a size of 0.4 inches, redback spiders are black with a red stripe or hourglass on their backs. They are not aggressive and will play dead if provoked; however, females will bite in defense of their eggs. Redback spider venom contains alpha-latrotoxins targeting the nervous system causing pain, elevated heart rate, sweating, and lymph node swelling.

7. Wandering Spider

brazilian wandering spider fangs
The Brazilian wandering spider raising its legs

The Brazilian wandering spider is also known as the banana spider or armed spider. It is a highly venomous arachnid that inhabits humid and tropical forests in Central and South America. These large spiders have a leg span of up to 7 inches and red hair covering their fangs. Brazilian wandering spiders rank at the top of the world’s 10 most venomous spiders. They carry a potent neurotoxic venom that causes immense pain and symptoms such as abdominal cramps, excessive sweating, convulsions, and shock.

8. Brown Widow Spider

brown widow spider markings
The brown widow spider has orange and brown spots

Brown widows belong to the same family as black widow spiders and are tan or black in color with orange, white, or yellow markings on the abdomen. The venom of a brown widow spider is described as more powerful than the black widow. But their small size means that their bites contain a very small amount of venom. The brown widow is found in South Africa, America, Japan, and parts of Australia.

9. Red Widow Spider

red widow spider web
The red widow spider spins her web

The female red widow spider is one of the most dangerous spiders in the world. Easily identified by its red legs and black bottom covered in orange spots, it is endemic to Florida. Red widows only bite when threatened or pressed against the skin. They have a neurotoxic venom that leads to muscle spasms, pain, and the possibility of permanent nerve damage.

10. Sicarius Spiders

Sicarius spider in desert
Sicarius spiders have the perfect camouflage

Sicarius spiders have a dermonecrotic venom that can damage the skin, blood vessels, and organs of the body. Two of the most toxic Sicarius spider species include the six-eyed sand spider (Sicarius hani) and Sicarius terrosus or thomisoides. Sicarius hani is found in Southern Africa, reaching 3 inches in length, while Sicarius terrosus inhabits Chile. These arachnids are red to brown in color with a flat shape to camouflage themselves in the desert sand.

Lisa Szymanski
By Lisa Szymanski

Lisa is a wildlife enthusiast who enjoys hiking and gardening and has four years of experience volunteering at pet shelters. She is the proud mom of two dogs, a Pitbull named Ragnar, a Boerboel named Blueberry, and four feisty chickens, or as she calls them, the "queens of the yard," Goldie, Gray, Peaches, and Brownie.