Juliette Nadia Boulanger (French: [ʒyljɛt nadja bulɑ̃ʒe] ^ⓘ; 16 September 1887 – 22 October 1979) was a French music teacher, conductor and composer. She taught many of the leading composers and musicians of the 20th century, and also performed occasionally as a pianist and organist.

From a musical family, she achieved early honours as a student at the Conservatoire de Paris but, believing that she had no particular talent as a composer, she gave up writing music and became a teacher. In that capacity, she influenced generations of young composers, especially those from the United States and other English-speaking countries. Among her students were many important composers, soloists, arrangers, and conductors, including Grażyna Bacewicz, Daniel Barenboim, Lennox Berkeley, İdil Biret, Elliott Carter, Aaron Copland, David Diamond, John Eliot Gardiner, Philip Glass, Roy Harris, Quincy Jones, Gilbert Levine, Dinu Lipatti, Igor Markevitch, Julia Perry, Astor Piazzolla, Laurence Rosenthal, and over 250 others.

Boulanger taught in the U.S. and England, working with music academies including the Juilliard School, the Yehudi Menuhin School, the Longy School, the Royal College of Music and the Royal Academy of Music, but her principal base for most of her life was her family's flat in Paris, where she taught for most of the seven decades from the start of her career until her death at the age of 92.

Boulanger was the first woman to conduct many major orchestras in America and Europe, including the BBC Symphony, Boston Symphony, Hallé, and Philadelphia orchestras. She conducted several world premieres, including works by Copland and Stravinsky.

Nadia Boulanger was born in Paris on 16 September 1887, to French composer and pianist Ernest Boulanger (1815–1900) and his wife Raissa Myshetskaya (1856–1935), a Russian princess, who descended from St. Mikhail Tchernigovsky.

Ernest Boulanger had studied at the Paris Conservatoire and, in 1835 at the age of 20, won the coveted Prix de Rome for composition. He wrote comic operas and incidental music for plays but was most widely known for his choral music. He achieved distinction as a director of choral groups, teacher of voice, and a member of choral competition juries. After years of rejection, in 1872 he was appointed to the Paris Conservatoire as professor of singing.

Raissa qualified as a home tutor (or governess) in 1873. According to Ernest, he and Raissa met in Russia in 1873, and she followed him back to Paris. She joined his voice class at the Conservatoire in 1876, and they were married in Russia in 1877. Ernest and Raissa had a daughter, Ernestine Mina Juliette, who died as an infant before Nadia was born on her father's 72nd birthday.

Through her early years, although both parents were very active musically, Nadia would get upset by hearing music and hide until it stopped. In 1892, when Nadia was five, Raissa became pregnant again. During the pregnancy, Nadia's response to music changed drastically. "One day I heard a fire bell. Instead of crying out and hiding, I rushed to the piano and tried to reproduce the sounds. My parents were amazed." After this, Boulanger paid great attention to the singing lessons her father gave, and she began to study the rudiments of music.