Botulism (Latin, botulus, "sausage") (pronounced /ˈbɒtʃʉlɪsəm/) also known as botulinus intoxication is a rare but serious paralytic illness caused by botulinum toxin which is metabolic waste produced under anaerobic conditions by the bacterium Clostridium botulinum, and affecting a wide range of mammals, birds and fish.

The toxin enters the human body in one of three ways: by colonization of the digestive tract by the bacterium in children (infant botulism)^{[citation needed]} or adults (adult intestinal toxemia), by ingestion of toxin from foods (foodborne botulism) or by contamination of a wound by the bacterium (wound botulism). Person to person transmission of botulism does not occur.

All forms lead to paralysis that typically starts with the muscles of the face and then spreads towards the limbs. In severe forms, it leads to paralysis of the breathing muscles and causes respiratory failure. In light of this life-threatening complication, all suspected cases of botulism are treated as medical emergencies, and public health officials are usually involved to prevent further cases from the same source.