Rabbi Judah haNasi, or more accurately in Hebrew, Rabbi Yehudah HaNasi, was a key leader of the Jewish community of Judea under the Roman empire, toward the end of the 2nd century CE. He was reputedly from the Davidic line of the royal line from King David, hence his title "Prince" (Nasi, also a "President" in modern terminology.)

His name is usually translated into English as Judah the Prince. He is also referred to as Rabbeinu HaKadosh (Our holy rabbi), and as Rebbi ([My] rabbi or teacher),

He is best known in Judaism as the chief "editor" or "redactor" of the Mishnah, the first part of the written compendium of Jewish religious law known as the Oral Law or Torah SheBe'al Peh upon which the Talmud is based and from which classical Jewish law Halakha is derived.

Biography

Little firm data is available on Rabbi Judah's life; the Mishnah and Talmud contain no serious biographical studies of the rabbis, and the same tractate will conflate the points of view of many different people.

Modern historians find it difficult to separate fact from legend, and many have given up on the idea that one can write an accurate biography of Mishnaic rabbis. At best, they hold, one can recover the basic outline of a rabbi's life as recalled by later sages, and this outline can be studied in a historical perspective. Most Orthodox Jews view the biographical statements in the Mishnah, Talmud and in some cases, even the early midrash collections, as being entirely historically reliable.

According to a statement handed down in Palestine (by Abba ben Kahana, Midrash Genesis Rabbah lviii.; Midrash Eccl. Rabbah i. 10) and in Babylonia (Ḳid. 72b), Judah I. was born on the same day on which Akiba died a martyr's death. The place of his birth is not known; nor is it recorded where his father, Simon b. Gamaliel II., sought refuge with his family during the persecutions under Hadrian.

On the restoration of order in Palestine, Usha became the seat of the academy and of its director; and here Judah spent his youth. It may be assumed that his father gave him about the same education that he himself had received, and that his studies included Greek (Talmud Sotah 49b); indeed, his knowledge of Greek fitted him for dialogue with the Roman authorities. He had a predilection for this language, saying that the Jews of Palestine who did not speak Hebrew should consider Greek as the language of the country, while Syriac (Aramaic) had no claim to that distinction (Sotah ib.). In Judah's house pure Hebrew seems to have been spoken; and the choice speech of the "maids of the house of Rabbi" became famous (Meg. 18a; R. H. 26b; Naz. 3a; 'Er. 53a).