Nida Eliz Üstündağ (born 21 October 1996) is a Turkish swimmer specialized in butterfly stroke.

[3][4] After graduation from Ankara Atatürk High School, she entered Başkent University to study Psychology.

[5][6] Üstündağ competed for Ankara University before she transferred to Galatasaray Swimming.

[7][8] She took part at the 2016 European Aquatics Championships in London, United Kingdom and placed 44th in the women's 50 m butterfly event.

[3] She earned a quota spot to compete for Turkey in the women's 200 m butterfly event at the 2016 Summer Olympics.