A lionfish, alternatively called dragon fish, scorpion fish, or turkey fish, is a venomous tropical marine fish noted for its long, separated spines. Lionfish is not a single fish species, but rather incorporates many species of the family Scorpaenidae. Many people enjoy the appearance of lionfish, which are often brightly colored and striped, making them popular aquarium fish. Lionfish are often striped in some combination of brown, red, yellow, orange, black, and white.

Lionfish are native to the tropical waters of the Indo-Pacific region, but also live in coral regions of the Eastern Atlantic and the Caribbean. They tend to live around crevices and caves, where they spend most of the day. Lionfish are thought to be nocturnal. They are active predators with quick reflexes that feed on smaller fish. They use their poisonous spines to subdue their prey before swallowing it whole.

Though lionfish are relatively easy to care for as pets due to their hardiness, the possibility of being stung by their spines makes than an impractical choice of aquarium fish for many people. The sting of a lionfish is quite painful and often accompanied by swelling. Systemic symptoms consistent with shock can also occur, including dizziness, hypotension, shortness of breath, nausea, headache, and muscle weakness. Tissue necrosis at the site of the sting is rare, though possible. No deaths have been reported in humans as a result of lionfish venom.

The severity of lionfish venom varies according to the size and species of the fish. A lionfish sting can be treated with heat. Immersing the affected area in hot water, about 113° Fahrenheit (45° Celsius), for 30 to 40 minutes can alleviate the pain and swelling.

Lionfish is edible, and though it carries venom, preparing it safely is not difficult. This is because the venom is contained in the spines, rather than in the internal organs of the fish.