Lead poisoning, also known as plumbism and saturnism, is a type of metal poisoning caused by lead in the body. The brain is the most sensitive. Symptoms may include abdominal pain, constipation, headaches, irritability, memory problems, infertility, and tingling in the hands and feet. It causes almost 10% of intellectual disability of otherwise unknown cause and can result in behavioral problems. Some of the effects are permanent. In severe cases, anemia, seizures, coma, or death may occur.

Exposure to lead can occur by contaminated air, water, dust, food, or consumer products. Lead poisoning poses a significantly increased risk to children as they are far more likely to ingest lead indirectly by chewing on toys or other objects that are coated in lead paint. The amount of lead that can be absorbed by children is also higher than that of adults. Exposure at work is a common cause of lead poisoning in adults with certain occupations at particular risk. Diagnosis is typically by measurement of the blood lead level. The Centers for Disease Control and Prevention (US) has set the upper limit for blood lead for adults at 10 µg/dl (10 µg/100 g) and for children at 3.5 µg/dl, previously before October 2021 5 µg/dl Elevated lead may also be detected by changes in red blood cells or dense lines in the bones of children as seen on X-ray.

Lead poisoning is preventable. This includes individual efforts such as removing lead-containing items from the home, workplace efforts such as improved ventilation and monitoring, state and national policies that ban lead in products such as paint, gasoline, ammunition, wheel weights, and fishing weights, reduce allowable levels in water or soil, and provide for cleanup of contaminated soil. Workers' education could be helpful as well. The major treatments are removal of the source of lead and the use of medications that bind lead so it can be eliminated from the body, known as chelation therapy. Chelation therapy in children is recommended when blood levels are greater than 40–45 µg/dl. Medications used include dimercaprol, edetate calcium disodium, and succimer.

In 2016, lead is believed to have resulted in 540,000 deaths worldwide. It occurs most commonly in the developing world. There also are numerous cases in the developed world, with there being thousands of American communities with higher lead burdens than seen during the peak of the Flint water crisis. Those who are poor are at greater risk. Lead is believed to result in 0.6% of the world's disease burden. According to a study, half of the US population has been exposed to substantially detrimental lead levels in early childhood – mainly from car exhaust whose lead pollution peaked in the 1970s and caused widespread loss in cognitive ability.

People have been mining and using lead for thousands of years. Descriptions of lead poisoning date to at least 2000 BC, while efforts to limit lead's use date back to at least the 16th century. Concerns for low levels of exposure began in the 1970s with there being no safe threshold for lead exposure.