Reuven Fahn was born on 21 February 1878 in the village of Starunia in southeastern Austrian Galicia. Fahn could read and write in Hebrew, German, Yiddish, Polish, and Ukrainian by the age of 15. In 1897, at age 19, Fahn married Rachel Keren and moved to his wife's hometown, the Polish city of Halicz. In Halicz, Fahn was influenced by the Karaite Jewish community and their unique culture, which Fahn often wrote about in his literary works.