Most Poisonous and Venomous Fish in the World

Most Poisonous and Venomous Fish in the World


When you’re sitting on a beautiful beach looking out over the blue, rolling waves of the ocean, it’s easy to forget your troubles and worries. However, if you start to consider what lies in the deep, dark depths of that sea, you might not be happy to learn what’s lurking below. 

The ocean contains some of the world’s most dangerous, deadly, and unknown creatures. Our list of the most poisonous and venomous fish in the world could have you second-guessing that beach vacation. 

The Top 10 Most Poisonous and Venomous Fish

Below, you’ll find some of the most frightening fish who have uniquely deadly ways of taking the life of their prey – along with yours. From a jellyfish that can kill you with one zap to a camouflaged fish that can cause cardiac arrest, this list is not one you want to ignore. 

1. Cubozoa

The Cubozoa is most widely known as the box jellyfish. This beautiful, delicate-looking creature is anything but when you consider just how deadly it is. A reasonably large animal, the box jellyfish can weigh almost five pounds, and its many delicate tentacles can be as long as about ten feet. 

Though almost elegant in appearance, the box-shaped invertebrate is considered to be one of the most toxic animals in the world. With a single sting, it can transfer potent venom that instantly stuns or kills its prey. 

One sting contains deadly toxins that directly attack the heart, the nervous system, and the skin cells. While this sting is most commonly used for the jellyfish to attack its prey for food, a sting to a human can be deadly. 

The venom is so powerful and painful that most human victims cannot make it to the shore before they die. They’re likely to go into shock and drown or die of heart failure. 

It’s possible for a person to survive a Cubozoa sting; however, one can expect a nasty scar to go along with weeks of intensive pain. The jellyfish causes as many as 40 deaths per year in the Philippines. 

2. Pufferfish

Pufferfish are distinctive sea creatures known for their ability to puff up their body, expanding an array of 360-degree quills to scare off their enemies. But did you know that these fish can be quite deadly? 

The pufferfish contains a dangerous toxin called tetrodotoxin. It runs throughout the animal’s entire body and is derived from bacteria. This toxin is up to 1,200 times more poisonous than cyanide, and one fish has the potential to kill 30 adult humans – with no antidote. 

That being said, the meat from this extraordinary being is actually considered a delicacy. That’s right – this super-poisonous fish deadly to humans doubles as a meal that people enjoy, especially in Japan. 

Not only is this meal costly, but it takes a highly trained, licensed chef to prepare it. That’s because it must be prepared in a specialized way to ensure all of the toxins are removed. 

Although there are trained individuals who are experts in the topic, there are still several deaths that occur from eating this fish annually. Only a real daredevil would give this meal a shot. 

3. Zebra Surgeon Fish

Boasting stripes that rival those of the mammal we all know and love, the zebra, this eye-catching fish isn’t as innocent as it may appear. You may not notice from afar, but the sea creature possesses an erectile spine that’s as sharp as a scalpel. 

The spine sits at the base of the caudal fin and contains powerful, dangerous venom. It cuts into any prey who dares to get too close. In fact, this fish is known to be overly aggressive and will attack any animal or person who comes its way. 

Despite the deadly knife-like fin, the Zebra Surgeon Fish is actually edible. Many enjoy the fish, but there’s still some risk to consuming it. It’s been known to cause a special kind of food poisoning called ciguatera. Ciguatera causes face numbness, itching, and in severe cases, hypotension and a slowing of the heart rate. 

4. Crown of Thorns Fish

The crown of thorns fish is actually a starfish, and it’s the only starfish in the whole world that is poisonous. Appropriately named, this spikey animal is covered with prickly spines. These sharp needle-like attachments can grow to be as long as two inches, and the fish itself can have anywhere from 7 to 23 arms. 

A beautiful contribution to the coral reefs, the crown of thorns fish come in a wide variety of colors. You might see an average brown one, or brighter colors like green and purple with red, yellow, or blue spines. 

While not necessarily deadly, the spines of this starfish can impact human health. If you get pricked by one of them, you may experience pain, nausea, and vomiting. Redness and swelling at the injury site are also common. 

5. Stingray

For the most part, stingrays are considered calm and docile animals. They do not have a reputation for actively seeking out humans with the intention of causing them harm. 

However, they do have a strong reaction in terms of defensiveness, and that attack can be deadly. 

You may remember Crocodile Hunter Steve Irwin. This animal-obsessed, Australian zookeeper handled some of the most dangerous animals in the world, until he was fatally attacked by a stingray in a horrible accident. 

Most stingray injuries happen below the knee on people who were just in the wrong place at the wrong time. In most cases, death is extremely rare. While a stingray does contain venom, it’s not usually deadly. 

But if a stingray strikes you in the chest or abdomen with its sharp tail, it could kill you. A hit directly to the heart would most certainly be fatal. Any other kind of piercing can cause severe muscle contractions, which are very painful. It can also cause tissue or cell death. 

6. Boxfish 

Given the close relation of the boxfish to the pufferfish, it shouldn’t come as a surprise that this square-looking fish is also poisonous. Don’t jump to conclusions here – this fish is not nearly as poisonous as the pufferfish. But, it’s still best to keep your distance.

The boxfish’s odd shape and fashionable appearance make it look harmless. It’s bright yellow color is certainly eye-catching, and it sports adorable black polka dots all over. 

However, this fish has been known to excrete a dangerous toxin whenever it feels threatened or scared. Their skin cells release this toxin into the water, which will poison anything in the surrounding area. 

The toxin can break down and destroy red blood cells, which can be harmful to both marine life and humans who get too close.   

7. Candiru 

The Candiru is a fish found native to the Amazon River region. It is uncanny in its similarity to an eel, as it boasts a translucent appearance and does not have scales as other fish do. 

This tiny fish is only about one inch long, so it’s difficult to even see it in the water. This fish doesn’t possess any poison, but it is quite deadly. It’s a parasitic catfish that likes to latch on to the gill cavities of other fish, feeding on their blood. 

When the Candiru decides to make a human its prey, it will actually enter the body through a person’s urethra. Once inside, it lets loose its short spines, which attach it to the victim and cause inflammation. It can also cause hemorrhaging and eventually even death.  

8. Lionfish

The lionfish is one that is quite impressive in terms of appearance. Entirely covered in brown and white strips, the fish boasts larges, billowing fins that flow gracefully through the water. 

Though its fins are nice to look at, we wouldn’t recommend getting near this big cat of the ocean. A highly toxic animal, the lionfish has venom within its dorsal spines. 

Thankfully, the fish is not known to be aggressive whatsoever. In fact, it is actually a rather timid fish who likes to mind its own business. The dorsal spines simply act as a defense mechanism to protect him when predators get too close. 

It’s best to stay far from these guys – contact with that dorsal fin results in a strong poison that can cause severe pain, vomiting, shortness of breath, and eventually paralysis of every muscle in the human body. Once the cardiac muscle is impacted, the result is death. 

9. Stonefish

The stonefish is not a particularly attractive fish, but don’t say that to its face. Hidden in the Red Sea and the Indo-Pacific, this fish houses 13 dorsal spines that are very much venomous. 

The fish can be challenging to spot, as it likes to hide on the seabed. It accomplishes excellent camouflage by burying itself in the sand or hiding within the rocks. When all is said and done, it merely looks like another stone in the ocean.

A sting from one of these many spines can cause a person to lose consciousness. That alone is a threat when you’re at the bottom of the ocean. Plus, the venom can also cause cardiac arrest.

(You might also be interested in reading about the Most Dangerous Fish in the Ocean)

10. Viperfish

Many people fear the deepest depths of the ocean because it’s pitch black and relatively unknown. However, some fear this region of the world because of what we do know – like the viperfish. 

The deepsea dwelling fish has a nasty appearance, full of gnarly, jagged teeth that reach both inside and outside of its mouth. 

Its appearance alone is enough to scare anyone who encounters this fish, but it’s also one of the most poisonous fish you can find in the ocean. 

The viperfish is most well known for its light-producing organ, which hangs from a line over its head. The light serves to attract other fish. The viperfish lies completely still as its prey approaches the light, and then it strikes. 

While extraordinarily poisonous and deadly, this fish lives far deeper than you will probably ever go in the ocean. Plus, it’s really only interested in its next meal, not humans. 

(Fishing in Freshwaters? You must know about the Most Dangerous Freshwater Fish)


Whether from a sting directly to the heart of an innocent meal in a foreign country, any one of these extremely poisonous and venomous creatures could be the last thing you encounter alive. We can certainly still enjoy the beauty, mystery, and intrigue of the ocean – but sometimes it’s best done from afar. 

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