The most deadly animal in Australia is the horse, which has caused almost a third of deaths by animals over the past 20 years, accounting for 222 deaths, mostly from falls. However, the most venomous animal in the world is the box jellyfish, which can kill a human in minutes due to its potent venom. Despite the high number of deaths caused by horses, the box jellyfish is considered the most dangerous marine creature in Australia, particularly active in coastal waters from October to May.