Marta Vadymivna Fiedina (; born 1 February 2002) is a retired Ukrainian synchro swimmer. She is a twice Olympic bronze medalist.
At the 2020 Summer Olympics (postponed to 2021 because of the COVID-19 pandemic), Fiedina and her duet partner Anastasiya Savchuk won Ukraine's first-ever Olympic medal in artistic swimming, scoring a total of 189.4620 in the combined technical and free routines on 4 August. On 7 August, she was part of the Ukrainian team that finished third in the final with a total score of 190.3018, earning her a second bronze medal.
She won the silver medal in the solo technical routine at the 2022 World Aquatics Championships held in Budapest, Hungary.