The world's deadliest spider is the Brazilian huntsman Phoneutria fera. This spider has the most active neurotoxic venom of any spider in the world, with only 0.006 milligrams being enough to kill a mouse.
This spider is a member of the Brazilian wandering spiders of the genus Phoneutria. The spider is dark in color and is extremely aggressive, often entering human dwellings. The average Brazilian huntsman spider has a body-and-leg spread of approximately 6.75 inches. An antivenom is available for this spider. Other extremely poisonous spiders include the black widow spider (Latrodectus mactans), wolf spider (family Lycosidae) and yellow sac spider (Cheiracanthium inclusum).