William Griffith Wilson (November 26, 1895 – January 24, 1971), also known as Bill Wilson or Bill W., was the co-founder of Alcoholics Anonymous (AA).

AA is an international mutual aid fellowship with about two million members worldwide belonging to approximately 10,000 groups, associations, organizations, cooperatives, and fellowships of alcoholics helping other alcoholics achieve and maintain sobriety. Following AA's Twelfth Tradition of anonymity, Wilson is commonly known as "Bill W." or "Bill." In order to identify each other, members of AA will sometimes ask others if they are "friends of Bill". Although this question can be confusing, because "Bill" is a common name, it does provide a means of establishing the common experience of AA membership. After Wilson's death in 1971, and amidst much controversy within the fellowship, his full name was included in obituaries by journalists who were unaware of the significance of maintaining anonymity within the organization.Wilson's sobriety from alcohol, which he maintained until his death, began December 11, 1934. In 1955 Wilson turned over control of AA to a board of trustees. Wilson died in 1971 of emphysema complicated by pneumonia from smoking tobacco. In 1999 Time listed him as "Bill W.: The Healer" in the Time 100: The Most Important People of the Century.