Oksana Rubaniak was born on 28 January 2003 in the village of Hramotne, now the Biloberizka community of Verkhovyna district, Ivano-Frankivsk region, Ukraine.
She graduated from the Ivano-Frankivsk College of Vasyl Stefanyk Precarpathian National University (2022, with honours, speciality - primary school teacher), the Military Department of PNU (2023), and the Mykhailo Drahomanov National Pedagogical University (part-time). Since 2022, she has been studying at the Vasyl Stefanyk Precarpathian National University, specialising in Public Administration and Management.
She worked as an external specialist at the Department of Youth Policy and Sports of Ivano-Frankivsk City Council. She was an organiser of MMA competitions among military personnel.
On 24 February 2022, she joined the Volunteer Formation of the Ivano-Frankivsk Territorial Community No. 3, and then the Armed Forces of Ukraine. She is the only woman among the servicemen of the machine gun platoon of the 72nd separate mechanised brigade. She performed combat missions at the Vuhlehirska TPP, Zaitsevo, as well as on the Bakhmut, Maryansky and Vuhledar directions.
In March 2023, she was seriously injured in Vuhledar. At the end of June of the same year, she returned to the front.