Thoroughly Modern Millie is a musical with music by Jeanine Tesori, lyrics by Dick Scanlan, and a book by Richard Morris and Scanlan. It is based on the 1967 film of the same name, which itself was based on the British musical Chrysanthemum, which opened in London in 1956. Thoroughly Modern Millie tells the story of a small-town girl, Millie Dillmount, who comes to New York City to marry for money instead of love – a thoroughly modern aim in 1922, when women were just entering the workforce. Millie soon begins to take delight in the flapper lifestyle, but problems arise when she checks into a hotel owned by the leader of a white slavery ring in China. The style of the musical is comic pastiche. Like the film on which it is based, it interpolates new tunes with some previously written songs.

Jeanine Tesori, known earlier in her career as Jeanine Levenson, is an American composer and musical arranger best known for her work in the theater. She is the most prolific and honored female theatrical composer in history, with five Broadway musicals and six Tony Award nominations. She won the 1999 Drama Desk Award for Outstanding Music in a Play for Nicholas Hytner's production of Twelfth Night at Lincoln Center, the 2004 Drama Desk Award for Outstanding Music for Caroline, or Change, the 2015 Tony Award for Best Original Score for Fun Home, making them the first female writing team to win that award, and the 2023 Tony Award for Best Original Score for Kimberly Akimbo. She was named a Pulitzer Prize for Drama finalist twice for Fun Home and Soft Power.