Alcoholics Anonymous (AA) is an international mutual aid fellowship of alcoholics dedicated to abstinence-based recovery from alcoholism through its spiritually-inclined Twelve Step program. Following its Twelve Traditions, AA is non-professional, non-denominational, as well as apolitical and unaffiliated. In 2020 AA estimated its worldwide membership to be over two million with 75% of those in the U.S. and Canada.

AA has maintained neutrality towards the disease model of alcoholism though its program is sympathetic to it, but its wider acceptance has been partly due to many AA members independently promulgating it. Regarding its effectiveness, a recent scientific review saw interventions encouraging increased AA participation resulting in higher abstinence rates than other interventions.

1935 is marked by AA as its starting year when a newly sober Bill Wilson (Bill W.) first commiserated with the alcoholic Bob Smith (Dr. Bob) and brought him into AA’s precursor the Christian revivalist Oxford Group. Leaving the Oxford Group to form a fellowship of alcoholics only, Wilson and Smith, along with other early members, wrote Alcoholics Anonymous: The Story of How More Than One Hundred Men Have Recovered From Alcoholism, from which AA acquired its name. Published in 1939 and commonly called "the Big Book", it contains AA's Twelve Step recovery program. Later editions included the Twelve Traditions, first adopted in 1946 to formalize and unify the fellowship as a benign anarchy.

The Twelve Steps are presented as a suggested self-improvement program of initially admitting powerlessness over alcohol and acknowledging its damage, the listing of and striving to correct personal failings and the making of amends for past misdeeds. To stay recovered, they suggest maintained spiritual development and the taking of other alcoholics through the Steps. Though not explicitly suggested, the latter is often done by sponsoring other alcoholics. The Steps do urge submission to the will of God—"as we understood Him"—but are accepting and accommodating to the practices and convictions of other spiritual persuasions as well as those of non-theist members.

The Twelve Traditions are AA's guidelines for members, groups and its non-governing upper echelons. Besides making a desire to stop drinking as the only requirement for membership, the Traditions advise against dogma, hierarchies and involvement in public controversies while mindful that helping others recover from alcoholism is AA’s primary purpose. Without threat of retribution or means of enforcement, the Traditions urge members to remain anonymous in public media. They also wish that members or groups to not use AA to gain wealth, property or prestige. Within AA, groups are autonomous, self-supporting through members’ voluntary contributions and obliged to reject outside contributions. Externally, no AA entity can represent AA as affiliated with or in support of other organizations or causes.

With AA's permission, subsequent fellowships such as Narcotics Anonymous and Gamblers Anonymous have adopted and adapted the Twelve Steps and the Twelve Traditions to their addiction recovery programs.