Ona Mimaitė was born in Rundžiai village, Žemaitkiemis rural district, Ukmergė county. In 1936, Ona started the primary school in Žemaitkiemis. After the fifth form, in 1941, she was admitted to the gymnasium in Ukmergė which she finished in 1948. While there, she took part in history and literature school clubs. Upon finishing school, Ona became a student at the faculty of History and Philology of Vilnius University. Her studies, however, were terminated by exile: in 1949, Ona and her sister were deported to Irkutsk region. In 1956 she wrote to the university asking for her school-leaving certificate which she intended to submit to another educational institution. Ona Mimaitė returned from exile after almost ten years.