Marianela Núñez (born 23 March 1982) is an Argentine-British ballet dancer. She is a principal dancer with The Royal Ballet, London. She has three brothers, all older than she is. Her mother sent her to ballet classes when she was three. At first, she took dance classes at her teacher's garage. At age five, Núñez decided to focus on ballet. She entered Teatro Colón Ballet School at age six.

In 2001, Núñez replaced the injured Leanne Benjamin as Kitri in Don Quixote, with Carlos Acosta as Basilio.[6] She was promoted to the principal dancer the following year. She has danced leading roles in both classical and contemporary works, by choreographers including Frederick Ashton, John Cranko, Kenneth MacMillan, Wayne McGregor and Christopher Wheeldon. In 2013, she won the Laurence Olivier Award for Outstanding Achievement in Dance for Viscera, Aeternum and 'Diana and Actaeon' from Metamorphosis: Titian 2012.

In 2018, following a performance of Giselle, Núñez celebrated her 20th anniversary at the Royal Ballet. Artistic director Kevin O'Hare declared her "one of the greats of her generation".

Outside the Royal Ballet, Núñez has made many guest appearances worldwide, including in Austria, U.S., Italy, Argentina and Australia. She had performed in La Scala Theatre Ballet many times, and is a frequent collaborator of Roberto Bolle. She had also returned to Colon Theater Ballet, where her career started.