Olha Petrovna Kosach-Kryvyniuk (Ukrainian: Ольга Косач-Кривинюк; May 26, 1877 – November 11, 1945) was a Ukrainian writer, translator, and physician. A member of the Prosvita cultural movement, she worked to establish a Ukrainian literary tradition through completing Ukrainian-language translations of Russian, French, and English literature under the pseudonym Olena Zirka. Her efforts to document the life and work of her sister, the poet Lesya Ukrainka, culminated in an extensive chronology that was published posthumously in 1970.