An envenomation is the process by which a venom or toxin is injected into another being via a bite, puncture or sting. Envenomation is always due to direct contact with an animal (or parts of it like drifting jellyfish tentacles). There are two possible mechanisms of injection: active, such as jellyfish or cone snails, or passive like lionfish or sea urchins. Injuries typically occur by incidental contact or deliberate attempts to handle a specimen. Envenomations are rare but can be life threatening and may require rapid first aid response. In this chapter, we will cover some common envenomations as well as some of the more rare, but serious cases.