Alcoholism is, broadly, any drinking of alcohol that results in significant mental or physical health problems. Because there is disagreement on the definition of the word alcoholism, it is not a recognized diagnostic entity, and the use of alcoholism terminology is discouraged due to its heavily stigmatized connotations. Predominant diagnostic classifications are alcohol use disorder (DSM-5) or alcohol dependence (ICD-11); these are defined in their respective sources.

Heavy alcohol use can damage all organ systems, but it particularly affects the brain, heart, liver, pancreas and immune system. Alcoholism can result in mental illness, delirium tremens, Wernicke–Korsakoff syndrome, irregular heartbeat, an impaired immune response, liver cirrhosis and increased cancer risk. Drinking during pregnancy can result in fetal alcohol spectrum disorders. Women are generally more sensitive than men to the harmful effects of alcohol, primarily due to their smaller body weight, lower capacity to metabolize alcohol, and higher proportion of body fat. In a small number of individuals, prolonged, severe alcohol misuse ultimately leads to cognitive impairment and frank dementia.

Environment and genetics are two factors in the risk of development of alcoholism, with about half the risk attributed to each. Stress and associated disorders, including anxiety, are key factors in the development of alcoholism as alcohol consumption can temporarily reduce dysphoria. Someone with a parent or sibling with an alcohol use disorder is three to four times more likely to develop an alcohol use disorder themselves, but only a minority of them do. Environmental factors include social, cultural and behavioral influences. High stress levels and anxiety, as well as alcohol's inexpensive cost and easy accessibility, increase the risk. People may continue to drink partly to prevent or improve symptoms of withdrawal. After a person stops drinking alcohol, they may experience a low level of withdrawal lasting for months. Medically, alcoholism is considered both a physical and mental illness. Questionnaires are usually used to detect possible alcoholism. Further information is then collected to confirm the diagnosis.

Prevention of alcoholism may be attempted by reducing the experience of stress and anxiety in individuals. It can be attempted by regulating and limiting the sale of alcohol (particularly to minors), taxing alcohol to increase its cost, and providing education and treatment.

Treatment of alcoholism may take several forms. Due to medical problems that can occur during withdrawal, alcohol cessation should be controlled carefully. One common method involves the use of benzodiazepine medications, such as diazepam. These can be taken while admitted to a health care institution or individually. The medications acamprosate or disulfiram may also be used to help prevent further drinking. Mental illness or other addictions may complicate treatment. Various forms of individual or group therapy or support groups are used to attempt to keep a person from returning to alcoholism. One support group is Alcoholics Anonymous, however the effectiveness of Alcoholics Anonymous is disputed.

The World Health Organization has estimated that as of 2016, there were 380 million people with alcoholism worldwide (5.1% of the population over 15 years of age). As of 2015 in the United States, about 17 million (7%) of adults and 0.7 million (2.8%) of those age 12 to 17 years of age are affected. Alcoholism is most common among males and young adults. Geographically, it is least common in Africa (1.1% of the population) and has the highest rates in Eastern Europe (11%). Alcoholism directly resulted in 139,000 deaths in 2013, up from 112,000 deaths in 1990. A total of 3.3 million deaths (5.9% of all deaths) are believed to be due to alcohol. Alcoholism reduces a person's life expectancy by approximately ten years. Many terms, some slurs and others informal, have been used to refer to people affected by alcoholism; the expressions include tippler, drunkard, dipsomaniac and souse. In 1979, the World Health Organization discouraged the use of alcoholism due to its inexact meaning, preferring alcohol dependence syndrome.