1. Inland taipan

Considered the most venomous snake in the world, the inland taipan has not in fact been known to have caused any human deaths. Its venom, containing neurotoxins (nerve damaging), myotoxins (muscle damaging) and procoagulants (disrupts blood clotting causing excessive bleeding), is more potent than that of any other snake in the world, and a bite is capable of killing more than 100 people.

It has an LD50 rating of 0.025 and an average venom yield of 44mg. The rapid delivery of venom – high in neurotoxins – can kill an adult in 45 minutes with symptoms including headache, nausea and paralysis. 

2. Geographer cone snail

One sting from a cone snail has the potential to kill 15 healthy adults within hours. The venom of the predatory cone snail, with an LD50 rating of 0.03, has neurotoxins that affect vision and speech. Only one recorded death has ever occurred in Australia – in 1935.

The most likely way to encounter this snail is by stepping on one, or picking up what looks like a pretty ‘shell’. Stings are often painless, and people may not realise at the time they have been stung. The cone snail has some unusual hunting apparatus: a harpoon-shaped proboscis used to entice and inject venom into its prey. 

3. Box jellyfish 

Often labelled the most lethal animal on the planet, the box jellyfish is capable of killing a healthy adult within minutes. There have been 79 confirmed deaths from this stinger since 1883 – and two from the Irukandji.

This predatory jellyfish has an LD50 rating of 0.04 and its venom contains hemotoxins (which affects the blood and attacks organs) and neurotoxins (which attack the brain), as well as dermatonecrotic substances (which cause scarring on the skin).

The box jellyfish has up to 60 tentacles, all with millions of tiny harpoons from which the venom is injected.

4. Eastern brown snake

Regarded as the second most venomous land snake in the world, with an LD50 rating of 0.053, the eastern brown snake is responsible for 24 known deaths since 1980. Its venom packs a powerful punch, made from a mix of neurotoxins, hemotoxins, procoagulants and nephrotoxins (damages kidney tissue) and is delivered in an average quantity of 2-6mg.

Its bite can cause cardiac arrest but more often leads to rapid and uncontrollable bleeding and kidney failure, with symptoms seen within 15 minutes of envenomation. On average, one to two people are killed by brown snakes every year – making it the most deadly snake in Australia.

5. Yellow-bellied sea snake

This snake is a true sea snake and like all highly venomous Australian snakes, it is from the elapid family. With an LD50 rating of 0.07, a bite from this snake yields a small amount of venom (1-4mg) but one that packs a punch, includings neurotoxins and myotoxins (which attack muscle).

Symptoms range from muscle stiffness and drooping eyelids to paralysis and death. However, no known fatalities have been recorded from this sea snake in Australia.

6. Coastal taipan 

Found along the coast from northern NSW to northern WA, coastal taipans are equipped with the longest fangs (up to 12mm) of any Australian snake and have the third most toxic venom of any land snake in the world.

With an LD50 rating of 0.099 and enough venom (120-400mg) to kill up to 12,000 guinea pigs in a single bite, the coastal taipan has been responsible for surprisingly few deaths. Its venom contains neurotoxins, hemotoxins and myotoxins which can cause rapid death in an adult in 30 minutes. Since the antivenom was developed in 1956 there have been no known deaths.

7. Common tiger snake

One of the most venomous land snakes in the world, the tiger snake is responsible for eight known deaths in Australia. With an LD50 rating of 0.118 and an average venom yield of 30-70mg, the tiger snake’s venom – containing neurotoxins, myotoxins and procoagulants – can trigger a severe reaction within 15 minutes, although antivenom is available. The most common symptoms are paralysis, muscle damage and uncontrollable bleeding. There is thought to be only one wide-ranging species of tiger snake that has great variation in size and colour.

8. Sydney funnel web spider 

Without doubt the deadliest spider in Australia, and probably the world, Sydney’s funnel web spider can kill an adult in an hour from just a single bite, using its venom which is high in neurotoxins.

Sydney’s funnel web spider has an LD50 rating estimated at 0.16 (unverified) and is responsible for 13 known deaths in Australia – although no deaths have been recorded since the antivenom was developed in 1981. Their bite, which yields an average dose of 0.14mg of venom, is extremely painful and can cause rapid and severe nerve stimulation resulting in muscle spasms and convulsions. Renowned for being aggressive and with fangs so large they can pierce through fingernails, this fearsome spider is found throughout bush and urban areas of NSW, and commonly found around suburban swimming pools.

9. Beaked sea snake

All 31 species of Australian sea snakes are venomous, and most of them are docile – but not the beaked sea snake. “They are the nastiest species of sea snake I’ve ever worked with,” says snake venom expert Assoc. Professor Bryan Fry.

With an LD50 rating of 0.164, the beaked sea snake’s venom contains a highly toxic dose of neurotoxins and myotoxins. A single bite can result in paralysis and muscle damage within six hours and delivers enough venom (7.9-9mg) to kill five adults. Previously thought to be one single species, it is now considered to be two species: one from Asia and one from Australia.

10. Blue-ringed octopus 

The last animal on the list may catch you off-guard, which is precisely why it is so dangerous. Unbeknownst to many, the blue-ringed octopus is highly venomous, with an LD50 rating of 0.300 and venom containing powerful neurotoxins called maculotoxins.

Responsible for two known deaths in Australia, their fast-acting venom can induce symptoms (muscular weakness, difficulty breathing and paralysis) within 10 minutes and death within 30 minutes, due to a complete lack of oxygen to the brain, unless CPR is commenced quickly. For such a small creature (25g), the blue-ringed octopus is powerful enough to kill 26 humans with one bite; but bites are uncommon, with no known deaths since the 1960s. There is no antidote.