Judah b. Hiyya (or Judah be-rabbi or Yehudah b. Hiyya; Hebrew: יהודה בריה דרבי חייא or יהודה בן רבי חייא) was a Jewish Amora sage of the Land of Israel, during the transitional period between the Tannaic and Amoraic eras. He was the son of R. Hiyya and his wife Judith, and the twin brother of Hezekiah.
His staements often are mentioned in the Talmud, especially in Order Kodashim.
Come of age he married the daughter of Rabbi Yannai. After he married, he went to study at a Beth midrash all week, and would return home every Sabbath eve, where a pillar of light moving before him. One of these times, he was so attracted by his subject of study that he had forgotten to return home, in order to perform his marital duties, the commandment of onah. When his father in-law, Rabbi Yannai, heard about it, he said he must be dead, since if he were to be alive he would not have neglected the performance of his marital duties. The sages of the Talmud explain that the satement of Rabbi Yannai was "like an error that proceedeth from the ruler", namely, The words of a Tzadik must come true even if he didn't intend them to be, and indeed Judah his son-in-law died.