Everything You Always Wanted to Know About Sex* (*But Were Afraid to Ask) is a book (1969, updated 1999) by California psychiatrist David Reuben. It was one of the first sex manuals that entered mainstream culture in the 1960s, and had a profound effect on sex education and in liberalizing attitudes towards sex. It was "among the top 20 all-time best sellers of the 20th century in the United States".