William Alan Finn is an American composer and lyricist. He is best known for his musicals, which include Falsettos, for which he won the 1992 Tony Awards for Best Original Score and Best Book of a Musical, A New Brain (1998), and The 25th Annual Putnam County Spelling Bee (2005).

Falsettos is a sung-through musical with a book by William Finn and James Lapine, and music and lyrics by Finn. The musical consists of March of the Falsettos (1981) and Falsettoland (1990), the last two installments in a trio of one-act musicals that premiered off-Broadway. The story centers on Marvin, who has left his wife to be with a male lover, Whizzer, and struggles to keep his family together. Much of the first act explores the impact his relationship with Whizzer has had on his family. The second act explores family dynamics that evolve as he and his ex-wife plan his son's bar mitzvah, which is complicated as Whizzer comes down with an early case of AIDS. Central to the musical are the themes of Jewish identity, gender roles, and gay life in the late 1970s and early 1980s.