Olha Petrivna Kosach (29 June 1849 – 4 October 1930), better known by her pen name Olena Pchilka (Ukrainian: ????? ??????), was a Ukrainian publisher, writer, ethnographer, interpreter, civil activist.
Sister of Mykhailo Drahomanov.
Mother of Lesya Ukrainka, Olga Kosach-Kryvyniuk, Mykhajlo Kosach, Oxana Kosach-Shymanovska, Mykola Kosach, Izydora Kosach-Borysova, Yurij Kosach.