The Sydney funnel-web spider (Atrax robustus) is a species of venomous mygalomorph  spider native to eastern Australia, usually found within a 100km (62mi) radius of Sydney. It is a member of a group of spiders known as Australian funnel-web spiders.  Its bite is capable of causing serious illness  or death in humans if left untreated.[3]

The lethal dose of venom in humans is not known. The lethal dose of venom from male Sydney funnel-web spiders for the crab-eating macaque (Macaca fascicularis) is 0.2 mg/kg. Higher figures were found for other experimental animals, such as 1.5 mg/kg for two-day-old mice. The average venom yield for a male  is 176 mg.[16] Guinness World Records has ranked the Sydney funnel-web as the world's most venomous spider, defining the term "most venomous" as "having the venom most toxic to humans",[17] although it has also given this title to the Brazilian wandering spider.[18]