The lead–crime hypothesis is the proposed link between elevated blood lead levels in children and increased rates of crime, delinquency, and recidivism later in life.

Lead is widely understood to be highly toxic to multiple organs of the body, particularly the brain. Individuals exposed to lead at young ages may be more vulnerable to learning disabilities, decreased I.Q., attention deficit hyperactivity disorder, and problems with impulse control, all of which may be negatively impacting decision making and leading to the commission of more crimes as these children reach adulthood, especially violent crimes.

Proponents of the lead–crime hypothesis argue that the removal of lead additives from motor fuel, and the consequent decline in children's lead exposure, explains the fall in crime rates in the United States beginning in the 1990s. This hypothesis also offers an explanation of the earlier rise in crime in the preceding decades as the result of increased lead exposure throughout the mid-20th century.

The lead–crime hypothesis is not mutually exclusive with other explanations of the drop in US crime rates....

State tests found more than 65,000 children in the city [Baltimore] with dangerously high blood-lead levels from 1993 to 2013. Across the United States, more than half a million kids are poisoned by lead each year, and the majority come from cities like Baltimore: rust belt towns built up during the first half of the 20th century when leaded paint was dominant. As populations and employment opportunities shrank in recent decades, poverty and neglect combined with older housing allowed lead paint poisoning to plague the city.