Nikki Blonsky is an American actress, singer, dancer, and internet personality. She is known for playing Tracy Turnblad in the film Hairspray (2007), for which she won two Critics' Choice Awards and nominations for a Golden Globe Award and a Screen Actors Guild Award.

Blonsky has starred as Willamena Rader in the ABC Family series Huge (2010), for which she received a Teen Choice Award nomination, had a recurring role as Margot on the series Smash (2013), and had roles in the films Geography Club (2013) as Therese and The Last Movie Star (2017) as Faith. She is a licensed cosmetologist.

Blonsky was born and raised in Great Neck, New York. She and her brother Joey  are the children of Karen, a school aide, and Carl Blonsky, a municipal worker for the village water pollution control district. Her father is Jewish, and her mother is Roman Catholic.

Blonsky attended Great Neck North Middle School and attended John L. Miller Great Neck North High School, and switched to Village School after a year at the latter. She additionally attended the after-school theatre program at William A. Shine Great Neck South High School daily, where she participated in productions of Les Misérables, Sweeney Todd, Kiss Me, Kate, and the title role of the opera Carmen.

Blonsky made her screen debut as Tracy Turnblad in the musical feature film Hairspray, which is an adaptation of the musical of the same name. She auditioned for the role as a high-school student with no professional acting or singing background at the time, and beat out eleven-hundred candidates. The film was released to commercial and critical success, and became Blonsky's first role. She received praise for her performance, with Roger Ebert of The Chicago Sun-Times writing "Without somebody like Nikki Blonsky at the heart of the movie, it might fall flat, but everybody works at her level of happiness..."  She received several awards and nominations, including winning two Critic's Choice Awards for Best Young Actress and Best Acting Ensemble,  and being nominated for the Golden Globe Award for Best Actress and the Screen Actors Guild Award for Outstanding Performance by a Cast in a Motion Picture.