Happy Birthday is a comedic stage play written by American playwright Anita Loos. The play premiered on Broadway at the Broadhurst Theatre in 1946. The show was nominated for two Tony Awards, Best Costumes by Lucinda Ballard and Best Lead Actress in a Play for Helen Hayes, who won the award as Addie Bemis. The plays tells the story of a librarian and her escapades when she decides to have a night on the town.^[1]

The play opened on October 31, 1946 at the Broadhurst Theatre to critical and financial success, extending its run and transferring to the Plymouth Theatre. The show closed its run on March 13, 1948 after 563 performances. The show was produced by Richard Rodgers and Oscar Hammerstein, who also wrote a song for the play titled "I Haven't Got a Worry in the World". The show was directed by Joshua Logan. Cloris Leachman served as Hayes' understudy. ^[2]