Blue-ringed octopuses Hapalochlaena (Cephalopoda: Octopoda: Octopodidae) live in shallow waters on rocky reefs in the intertidal and subtidal zones along the Australian coast. Their toxic saliva (venom) is used to subdue their prey of principally small crabs. The predominant toxin found in the saliva is tetrodotoxin (TTX), a sodium channel blocking neurotoxin, which causes dose-dependent muscle paralysis. The somewhat elusive Northern Australian Greater Blue-ringed Octopus Hapalochlaena sp. is attributed to the first documented human fatality (at East Point, Dawin, in 1954) from a blue-ringed octopus; however the octopus was not correctly identified until 1964. This paper clarifies the first documented fatality from a blue-ringed octopus envenoming and briefly reviews the literature on the natural history and toxicology of blue-ringed octopuses, focusing on the Northern Australian Greater Blue-ringed Octopus, the only species of Hapalochlaena in the Northern Territory.