Daniela Ruah

Ruah was born in Boston, U.S., to Jewish parents from Portugal, where her mother is an otologist and her father is an ENT surgeon. When Ruah was 5, the family moved back to Portugal, where she attended St Julian's School and, at 16, began acting in telenovelas. She won a Portuguese-television dance competition. Ruah moved to the UK at the age of 18 and earned a Bachelor of Arts in performing arts from London Metropolitan University. She returned to Portugal where she continued acting, and in 2007 moved to New York City to study at the Lee Strasberg Theatre and Film Institute. Ruah stated that she grew up in an environment that was both Sephardic and Ashkenazi; her father is of Portuguese-Jewish ancestry, and her mother's Jewish roots are in Russia, Ukraine and Portugal. She holds Portuguese and American citizenship.

Ruah started acting in Portuguese soap operas when she was a teen. She made her acting debut at 16, when she played Sara on the soap opera Jardins Proibidos ("Forbidden Gardens"). At 18, Ruah moved to London to attend college. After graduation, she returned to Portugal to pursue her acting career. She was the winner of the celebrity dance competition Dança Comigo (the Portuguese version of Dancing with the Stars) and got main roles in television series, short films, and theatre. In 2007, she moved to New York to study at the Lee Strasberg Theatre and Film Institute. Ruah starred as Special Agent Kensi Blye in NCIS: Los Angeles, which first aired on September 22, 2009. In 2011, she portrayed the character in a crossover guest appearance on the series Hawaii Five-0. While on NCIS in 2014 Ruah won an award for best on Best Prime-Time Television. In 2013, Ruah appeared in David Auburn's play Proof at Los Angeles' Hayworth Theatre. On January 8, 2018, it was confirmed that Ruah would co-host the Eurovision Song Contest 2018 in Lisbon, Portugal alongside Catarina Furtado, Sílvia Alberto and Filomena Cautela. In January 2026, Deadline Hollywood announced that Ruah would be producing and acting in a screen adaptation of Karen McQuestion's novel, The Moonlight Child. The project is slated for film with the title And Then She Was Gone, and will also feature her co-star from NCIS: Los Angeles, Natalia del Riego. The screenplay was written by Justin Kohlas who will executive produce under his KimberMark banner, alongside Ruah and Riccardo Maddalosso (Armageddon Time).

Ruah married David Olsen, the older brother and stunt double of Ruah's NCIS: Los Angeles co-star Eric Christian Olsen, in an interfaith ceremony on June 19, 2014. Olsen is Lutheran. They have a son, River Isaac Ruah Olsen (born December 30, 2013), and a daughter, Sierra Esther Ruah Olsen (born September 4, 2016).