Alcoholics Anonymous (AA) is a global peer-led mutual aid fellowship begun in the United States dedicated to abstinence-based recovery from alcoholism through its spiritually inclined twelve-step program. AA's twelve traditions, besides stressing anonymity, establish it as non-professional, unaffiliated, non-denominational, and apolitical with a public relations policy of attraction rather than promotion. In 2020, AA estimated a worldwide membership of over two million, with 75% of those in the US and Canada.

AA dates its founding to Bill Wilson’s (Bill W.) and Bob Smith’s (Dr. Bob) first commiseration alcoholic-to-alcoholic in 1935. Having met through AA's immediate precursor, the Christian revivalist Oxford Group, they and other alcoholics helped each other there until forming what became AA. At first only white and male, neither by design nor for long, the new fellowship published in 1939 Alcoholics Anonymous: The Story of How More than One Hundred Men Have Recovered from Alcoholism. Known as “the Big Book," it is also the origin of AA's name.

The Big Book debuted AA's suggested twelve steps as a continuing sobriety program of prayer, reflection, admission, better conduct, and atonement, all to produce a "spiritual awakening" followed by taking others—usually sponsees—through the steps. Divining and following the will of an undefined God—"as we understood Him" or as “a higher power”—is integral to the steps, but differing practices and beliefs, including those of atheists and other non-theists, are accommodated.

To keep sobriety as its primary purpose, AA instituted its twelve traditions in 1950 to ensure membership to all wishing to stop drinking without any dues or fees required. They urge all memberships to be kept anonymous, especially in public media, but when anonymity is broken, no consequences are prescribed. The traditions also have AA avoiding hierarchies, dogma, public controversies, and other outside entanglements as well as not acquiring property and for no members to use AA for material gain or public prestige. To stay independent and self-supporting, the traditions say no AA entity should accept outside financial aid.

For all demographics, a 2020 scientific review found clinical interventions increasing AA participation via AA twelve step facilitation (AA/TSF) had sustained remission rates 20-60% above other well-established treatments. Additionally, 4 of the 5 economic studies in the review found that AA/TSF lowered healthcare costs considerably. Regarding the disease model of alcoholism, an otherwise receptive AA has not endorsed it though many AA members have promoted it towards wider acceptance.

With AA’s permission, other recovery fellowships such as Narcotics Anonymous and Al-Anon have adopted and adapted the twelve steps and traditions.