Bronislava Nijinska (8 January 1891 {O.S. 27 December 1890}, Minsk, Russian Empire — 21 February 1972, Pacific Palisades, California) was a prominent Russian-American ballerina of Polish descent, renowned choreographer, and educator. She was the sister of famed dancer and choreographer Vaslav Nijinsky, and the mother of Irina Nijinska. Over a prolific career spanning more than two decades, Nijinska rose to international prominence with Serge Diaghilev's Ballets Russes, becoming increasingly involved as a choreographer and stage producer from the 1920s onward. Between 1925 and 1934, she toured extensively across the UK, Europe, and both North and South America, collaborating with notable figures and institutions including Teatro Colón, Opéra Russe à Paris, Ballet Russe De Monte Carlo, Anton Dolin, Alicia Markova's "London Festival Ballet," Hollywood Bowl, Jacob's Pillow, Max Reinhardt, and Le Marquis De Cuevas. During her career, she founded two ballet companies in Paris: Ballets Nijinska (1931) and Théâtre de la Danse Nijinska (1932–34). Nijinska immigrated to the United States in 1939 and became a naturalized citizen in 1949. Throughout her later years, she remained active as a choreographer and artistic director, devoting much of her time to teaching. Variations of her name include Branislava Nižynskaja, Bronislava Fominichna Nijinskaya, B. Fominitshna Nizhinskaya, Бронислава Фоминична Нижинская, and Браніслава Ніжынская.

Born in Minsk, now part of Belarus, Bronislava was the third child of Polish dancers who toured extensively. All of the children were baptized in Warsaw and grew up in Poland. Her older brother Vaslav Nijinsky (1889—1950) also gained fame as a ballet dancer and choreographer. Bronislava and Vaslav received their initial training from their parents, who operated a dance studio for both adults and children. Around 1900, at the age of nine, Bronislava began studying under the renowned Italian pedagogue Enrico Cecchetti. Following her brother's path, Nijinska enrolled in the Imperial Ballet School in Saint Petersburg, graduating with honors in 1908. That same year, she made her stage debut with the Mariinsky Ballet in Michel Fokine's Les Sylphides. Nijinska joined the Ballets Russes in 1910, debuting in Fokine's production of Carnaval, where the role of "Papillon" was created specifically for her. She assisted Vaslav Nijinsky with the controversial choreography of L'Après-midi d'un faune, which premiered at the Théâtre du Châtelet in May 1912. The following year, she again collaborated with her brother on the contentious Igor Stravinsky piece Rite of Spring, which ignited public unrest during its premiere due to its provocative costumes and Nijinsky's unconventional choreography. Bronislava Nijinska left the Ballets Russes upon discovering her pregnancy.

In 1914, she became part of the short-lived Saison Nijinsky company founded by her brother at the London Palace Theatre. The following year, Bronislava returned to Russia with her husband, splitting her time between Saint Petersburg and Kyiv, where she began designing and staging her own choreography. After the revolutions of 1917, the instability in Russia prompted her to expatriate in 1921. She rejoined Ballets Russes, where Diaghilev appointed her as a choreographer. In the ensuing four years, Nijinska created several innovative and critically acclaimed ballets, including Stravinsky's Les noces.