Content updated: July 8, 2026

Key takeaways

  • Most spiders are harmless, but certain venomous species like black widows, brown recluses, and Brazilian wandering spiders require medical treatment for bites.
  • Poisonous spider is technically inaccurate, as spiders are actually venomous creatures that inject toxins through a bite.
  • The Sydney funnel-web spider is the deadliest spider in the world due to its highly potent venom.
  • To help prevent encounters with spiders, clear away clutter, seal entry points, and do not handle spiders.
  • If you suspect a venomous spider is indoors or if a bite occurs, seek medical attention and professional pest control immediately.

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What is the deadliest spider in the world?

The most venomous spiders in the U.S. and abroad

Creepy – but not deadly – spiders in the U.S.

What should I do if I encounter a venomous spider?

What to do if you have a venomous spider bite

How can I prevent venomous spiders from getting into my home?

Most spiders aren't dangerous to people, but a few venomous spiders can cause bites that may need medical attention. Some of the best-known examples are black widows, brown recluses, Brazilian wandering spiders, and Sydney funnel-web spiders. While you might hear people call them 'poisonous,' spiders are actually venomous, which means they deliver toxins through a bite. Since many spiders can look alike, knowing how to identify them can help you decide when professional spider control may be necessary.

sydney-funnel-web

What is the deadliest spider in the world?

The Sydney funnel-web spider (Atrax robustus) is considered the world's most dangerous spider because its venom is extremely potent and can act quickly. Its venom has one of the lowest LD50 values among spiders, meaning it is highly toxic. According to the National Library of Medicine, before a dedicated antivenom was developed in 1981, the Sydney funnel-web spider had a high mortality rate, with the worst-case bites from aggressive males capable of causing death in as little as 15 minutes.

The most venomous spiders in the U.S. and abroad

Knowing how to identify venomous spiders, understanding where they live, and how dangerous they can be can help keep you safe. Common venomous spider species in the U.S. include the brown recluse and black widow, while the Brazilian wandering spider is common in Central and South America.

Brown recluse spider

Brown recluse spider (Loxosceles reclusa)

  • Danger level: Highly venomous; bites may cause skin necrosis.
  • Appearance: Tan to dark brown with a violin-shaped marking.
  • Size: Body ¼–½ inch; leg span up to 1½ inches.
  • Range: Central and southern U.S.
  • Behavior: Typically non-aggressive.
  • Bite symptoms: Redness, swelling, and localized blistering.
Black widow on leaves

Black widow spider (Latrodectus spp.)

  • Danger level: Highly venomous; severe symptoms possible.
  • Appearance: Glossy black with red or orange hourglass markings.
  • Size: Body ¼–â…– inch; leg span up to 1½ inches.
  • Range: Throughout the U.S.
  • Behavior: Not aggressive; bites defensively.
  • Bite symptoms: Muscle cramps, abdominal pain, nausea, and sweating.
brazilian-wandering-spider

Brazilian wandering spider (Phoneutria spp.)

  • Danger level: Extremely venomous; one of the world’s most dangerous spiders.
  • Appearance: Hairy brown/reddish body with dark markings.
  • Size: Body 1–1½ inches; leg span up to 6 inches.
  • Range: Central and South America.
  • Behavior: Aggressive when threatened.
  • Bite symptoms: Pain, sweating, muscle paralysis, and breathing difficulty.

Creepy – but not deadly – spiders in the U.S.

Nearly all spiders are technically venomous, using their venom to subdue prey, but for the vast majority, their venom poses little to no threat to humans. Most spider fangs are either too small to break human skin, or their venom is too weak to affect us.

giant-huntsman-spider

Giant huntsman spider

The giant huntsman spider holds the record for the longest leg span of any spider, measuring up to 12 inches across. While its size and speed can be startling, its venom poses no serious threat to humans.

goliath-birdeating-spider

Goliath birdeater

This is the largest spider in the world by weight, with a leg span that can reach up to 11 inches. On average, they weigh six ounces, which is around the same weight as a baseball or a large apple. Despite its intimidating name, its venom is not considered dangerous to humans.

wolf-spider-upclose

Wolf spider

These fast-moving hunters use venom to subdue prey, but their bites rarely cause serious harm to people; usually, they cause only mild irritation or swelling.

Yellow sac spider on leaf

Sac spiders

Sac spiders are small nocturnal hunters whose venom can cause mild skin irritation or small sores, but severe reactions are uncommon.

jumping spider

Jumping spiders

Known for their excellent vision and jumping ability, they have venom to immobilize insects. Their bites are rare and usually cause only slight discomfort.

False widow spider

False window spiders

False widow spiders are often mistaken for black widows because both are dark-colored and shiny, but false widows lack the distinctive red hourglass marking. Bites are uncommon and typically mild.

Cellar spider

Cellar spiders

Cellar spiders, also known as daddy long-leg spiders, are commonly found in basements, garages, and ceiling corners. Despite their spindly appearance, they are harmless to people and do not cause medically significant bites.

What should I do if I encounter a venomous spider?

If you encounter a venomous spider, there are a few steps you can take to help protect yourself, your pets, and your family.

  1. Stay calm and keep your distance: If you see a spider you suspect is venomous, do not try to touch, trap, or swat it. Quick movements may cause it to bite in self-defense. Step away slowly and give it space.
  2. Don’t attempt to handle it: Avoid handling the venomous spider yourself. If it’s indoors and you feel unsafe, call a Terminix spider pest control professional for proper identification and removal.
  3. Take notes of its appearance and location: If possible, take a picture from a safe distance for identification purposes. Note where you saw it in case it escapes before professionals arrive.

What to do if you have a venomous spider bite

A suspected venomous spider bite should be evaluated by a medical professional as soon as possible. In the meantime, there are steps you can take to help, including:

  • Wash the bite area thoroughly with soap and water.
  • Apply a cold compress or ice pack wrapped in a cloth to help reduce pain and swelling.
  • Elevate the affected arm or leg, if possible.
  • Remove rings, watches, or other tight items near the bite site in case swelling develops.
  • Monitor your symptoms closely and watch for worsening pain, swelling, or skin damage.
  • If it can be done safely, take a photo of the spider to help with identification.

Depending on the severity of symptoms, treatment may include pain management, wound care, and, in some cases, antivenom.

How can I prevent venomous spiders from getting into my home?

Securing your home requires eliminating entry points and reducing the habitats that attract arachnids and their insect prey. To help keep spiders out of your house, follow these simple tips:

  • Examine outdoor gear: Always shake out shoes, work gloves, boots, and seasonal clothing left in garages, mudrooms, or outdoors before putting them on.
  • Seal structural gaps: Apply caulk or weatherstripping to close gaps around window frames, doors, pipes, and foundation vents.
  • Clear clutter: Keep basements, attics, crawlspaces, and closets organized. Avoid storing items loosely on the floor.
  • Remove outdoor harborages: Cut back heavy vegetation that touches exterior walls and move firewood piles, leaf litter, and lawn debris away from your home’s foundation.

Professional spider control is the most effective way to address infestations and protect your home. With year-round coverage under our PestFree365+ plan, your home is continuously shielded from the most dangerous spider threats, including brown recluses and black widows. 1