According to multiple sources, including the World Health Organization and the BBC, the animal that kills the most humans per year is the mosquito. Mosquitoes can transmit life-threatening diseases like malaria and dengue, and the World Health Organization estimates that mosquitoes that carry these diseases kill between 725,000 and 1,000,000 people a year. Its worth noting that humans themselves are responsible for killing the most people every year, with an annual worldwide murder and suicide count of 530,000, as well as millions of unintentional fatalities caused by vehicular accidents and medical malpractice.