The Chicago Tylenol murders were a series of poisoning deaths resulting from drug tampering in the Chicago metropolitan area in 1982. The victims had all taken Tylenol-branded acetaminophen capsules that had been laced with potassium cyanide. A total of seven people died in the original poisonings, with several more deaths in subsequent copycat crimes.

To date, no suspect has been charged or convicted of the poisonings. New York City resident James William Lewis was convicted of extortion for sending a letter to Tylenol's manufacturer, Johnson & Johnson, that took responsibility for the deaths and demanded $1 million to stop them, but evidence tying Lewis to the actual poisoning never emerged.

The incidents led to reforms in the packaging of over-the-counter substances and to federal anti-tampering laws. The actions of Johnson & Johnson to reduce deaths and warn the public of poisoning risks have been widely praised as an exemplary public relations response to such a crisis.