Nida Eliz Üstündag (born October 21, 1996) is a Turkish female swimmer specialized in butterfly stroke.
She is a member of Galatasaray Swimming.She was born in Çanakkale on October 21, 1996.
After graduation from Ankara Atatürk High School, she entered Baskent University to study Psychology.Üstündag competed for Ankara University before she transferred to Galatasaray Swimming.In 2014, Üstündag competed in the girls' 50 m butterfly, 100 m butterfly and 200 m butterfly events at the Summer Youth Olympics in Nanjing, China.
She took part at the 2016 European Aquatics Championships in London, United Kingdom and placed 44th in the women's 50 m butterfly event.She earned a quota spot to compete for Turkey in the women's 200 m butterfly event at the 2016 Summer Olympics.