The Gemara (also transliterated Gemarah, or in Yiddish Gemo(r)re; from Aramaic גמרא‎, from the Semitic root ג-מ-ר gamar, to finish or complete) is the component of the Talmud comprising rabbinical analysis of and commentary on the Mishnah written in 63 books. At first, Gemara was only transmitted orally and was forbidden to be written down; however after the Mishnah was published by Judah the Prince (c. 200 CE), the work was studied exhaustively by generation after generation of rabbis in Babylonia and the Land of Israel. Their discussions were written down in a series of books that became the Gemara, which when combined with the Mishnah constituted the Talmud.

There are two versions of the Gemara. The Jerusalem Talmud (Talmud Yerushalmi), also known as the Palestinian Talmud, was compiled by Jewish scholars of the Land of Israel, primarily of the academies of Tiberias and Caesarea, and was published between about 350–400 CE. The Talmud Bavli (Babylonian Talmud) was published about 500 CE by scholars of Babylonia, primarily of the academies of Sura, Pumbedita, and Nehardea. By convention, a reference to the "Gemara" or "Talmud," without further qualification, refers to the Babylonian version. The main compilers were Ravina and Rav Ashi.

There are six groups of Gemara, namely Zeraim, Moed, Nashim, Nezikin, Kodshim and Taharot. There is a custom made in 1923 by Polish rabbi Meir Shapiro, who saw that there were parts of the Gemara that would never get read, so he started an initiative called Daf Yomi, where people learn a page of Gemara every day for seven years in order that the entire Gemara would be learned.