Yitzchak Yaakov Yellin (Hebrew: יצחק יעקב ילין, Isaac Jacob Yellin; 1885–1964) was one of the pioneers of the Hebrew language and press in Israel. He was one of the founders and editor of the daily newspaper "Moriah", as well as the editor of the weekly newspapers "Lefi Sha'a", "Be'inyaney Dyuma", and “Hed ha'am”. Yellin published Hebrew grammar books and was known as an educational figure who widely contributed towards the spread and use of the Hebrew language in Jerusalem of the early 20th century. He was also one of the founders of the Kiryat Moshe neighborhood in West Jerusalem.
Yellin was born in the Old City of Jerusalem to a family of famous biblical grammarians. His grandfather, Rabbi Shalom Shachne Yellin, who was known as "The Proofreader of Skidl", was regarded as one of the proofreaders of the most popular Torah books in the world, and his name is connected to the notes and commentary of the famous Aleppo Codex (Keter Aram Zoba) of Ben Asher. His uncle, Aryeh Leib Yellin, most known as the author of the Yefeh 'Enayim parallel passages of the Talmudic text, was a famous Polish rabbi. His father, a famous proofreader and Torah scribe, known by the alias Zvi Hirsch Sofer, was one of the founders of the Mishkenot Yisrael neighborhood in Jerusalem.
Yitzchak Yaakov Yellin married Lea Miriam, the daughter of Rabbi Meshulam Zalman Shapira, the son of Rabbi Haim Yaakov Shapira, the head of the Rabbinical Law Court of Jerusalem.
Already at 17 years of age, Yellin began publishing a weekly newspaper that was called The Zionist, in which he called upon the spreading of the Zionist idea and its adaptation by the Jewish Ultra-Orthodox wing, which he himself was part of. In “The Zionist”, which was distributed in yeshivas (Talmudic colleges) in Jerusalem, Yellin preached, among others, for Zionist achievements and the need of yeshiva students to join the work force.