Rabbi Elijah ben Shlomo Zalman, known as the Vilna Gaon or Elijah of Vilna and simply by his Hebrew acronym Gra ("Gaon Rabbenu Eliyahu"), (April 23, 1720 - October 9, 1797), was a Talmudist, halachist, kabbalist, and the foremost leader of world Jewry of the past few centuries. He is commonly referred to in Hebrew as haGaon haChasid miVilna, "the saintly genius from Vilnius." He was one of the most influential Rabbinic authorities since the Middle Ages, and, although he is counted among the sages known as the Acharonim, he is held by many authorities after him as belonging to the Rishonim (Rabbinic authorities of the Middle Ages). Large groups of people, including many yeshivas, uphold the set of Jewish customs and rites (minhag), the "minhag ha-Gra," which is named for him, and which is also considered by many to be the prevailing Ashkenazi minhag in Jerusalem.

Born in Vilnius, capital city of Grand Duchy of Lithuania, the Gaon displayed extraordinary talent while still a child. As young as three years old he had committed the Tanach to memory. At the age of seven he was taught Talmud by Moses Margalit, rabbi of Kedainiai and the author of a commentary to the Jerusalem Talmud, entitled "Pnei Moshe". The young Elijah was said to have already known several of the tractates by heart. He is well known for having possessed a photographic memory. By eight, he was studying astronomy during his free time. From the age of ten he continued his studies without the aid of a teacher, and by the age of eleven he had committed the entire Talmud to memory. When he reached a more mature age, Elijah decided to go into "exile" and he wandered in various parts of Europe including Poland and Germany, as was the custom of the pious of the time. By the time he was twenty years old, rabbis were submitting their most difficult halakhic problems to him. Scholars, Jewish and non-Jewish sought his insights into mathematics and astronomy. He returned to his native town in 1748, having by then acquired considerable renown.

He devoted much time to the study of the Torah and Hebrew grammar, and was knowledgeable in the secular sciences, enriching the latter by his original contributions. His pupils and friends had to pursue the same plain and simple methods of study that he followed. He also exhorted them not to neglect the secular sciences, maintaining that Judaism could only gain by studying them. The Gaon was also attracted to the study of Kabbalah. The Vilna Gaon was modest and he declined to accept the office of rabbi.

When Hasidic Judaism became influential in his native town, the Vilna Gaon, joining the rabbis and heads of the Polish communities, took steps to check the Hasidic influence. In 1777 one of the first excommunications was launched in Vilna against the Hasidim, while a letter was also addressed to all of the large communities, exhorting them to deal with the Hasidim following the example of Vilna, and to watch them until they had recanted. The letter was acted upon by several communities, and in Brody, during the merchant fair, the cherem (ban of excommunication) was pronounced against the Hasidim.

In 1781, when the Hasidim renewed their proselytizing work, the Gaon excommunicated them again, declaring them to be heretics with whom no pious Jew might intermarry. After this, the Gaon went into retirement again, and the Hasidim seized the opportunity to spread a rumor that he had sided with them and that he repented of having persecuted them. The Gaon then sent two of his pupils (1796) with letters to all the communities of Poland, declaring that he had not changed his attitude in the matter, and that the assertions of the Hasidim were pure inventions. However, the excommunications did not stop Hasidism.

Except for the conflict with the Hasidim, the Vilna Gaon almost never took part in public affairs and, so far as is known, did not preside over any school in Vilna. He was satisfied with lecturing in his bet hamidrash to a few chosen pupils, whom he initiated into his methods. He taught them Hebrew grammar, Tanach, and Mishna, subjects which were largely neglected by the Talmudists of that time. He was especially anxious to introduce them to the study of midrash literature, and the Minor Treatises of the Talmud, which were very little known by the scholars of his time.

He laid special stress on the study of the Jerusalem Talmud, which had been almost entirely neglected for centuries. Being convinced that the study of the Torah is the very life of Judaism, and that this study must be conducted in a scientific and not in a merely scholastic manner. As it states in the Mishna in Tractate Peah (1:1): "The study of Torah is equal to all of the mitzvos", the Gaon encouraged his chief pupil, Rabbi Chaim Volozhin, to found a yeshiva in which rabbinic literature should be taught. The yeshiva was opened at Volozhin in 1803, some years after the Gaon's death, and revolutionised Torah study, with resulting impacts on all of Orthodox Jewry.

The Vilna Gaon led an ascetic life. He interpreted literally the words of the Jewish sages, that the Torah can be acquired only by abandoning all pleasures and by cheerfully accepting suffering. And as he lived up to this principle, he was revered by his countrymen as a saint, being called by some of his contemporaries "the Hasid". This, of course, seems ironic, given his well known opposition to the Hasidic movement, though in fact the term is used in two different senses. The Gaon once started on a trip to the Land of Israel, but for unknown reasons did not get beyond Germany. In the early nineteenth century, three groups of his students, known as Perushim, did manage the trip, settling mostly in Tzfat and Jerusalem.

The Vilna Gaon was a voluminous author, there is hardly an ancient Hebrew book of any importance to which he did not write a commentary, or at least provide marginal glosses and notes, which were mostly dictated to his pupils. However, nothing of his was published in his lifetime. It must be noted that the "Gra" was very precise in the wording of his commentaries, because he maintained that he was obligated by Torah Law that only the "Torah shebichtav" (the written law) is permitted to be written down, the rest of "Torah she beal peh" (oral law) cannot be, unless circumstances require. So the Vilna Gaon abided by this view of law by reducing his extensive explanations that are largely inscrutable to any but advanced talmudists.

Glosses on the Babylonian Talmud and Shulchan Aruch are known as Biurei haGra ("Elaboration by the Gra"). His running commentary on the Mishnah is titled Shnot Eliyahu ("The Years of Elijah"). Various Kabbalistic works have commentaries in his name. His insights on the Pentateuch are titled Adereth Eliyahu ("The Splendor of Elijah"). Commentaries on the Proverbs and other books of the Tanakh were written later on in his life. He also wrote on mathematics, being well versed in the works of Euclid and encouraging his pupil Rabbi Baruch of Shklov to translate the great mathematician's works into Hebrew. A mathematical work titled Ayil Meshulash ("A Ram in Three Parts", a reference to Abraham's "Covenant Between the Parts" in Genesis 15:9) is generally attributed to him.

He was one of the most influential Rabbinic authorities since the Middle Ages, and, although he is counted as an Acharon, he is held by many authorities after him as belonging to the Rishonim (Rabbinic authorities of the Middle Ages). His main student Rabbi Chaim Volozhin, founded the first yeshiva in his home town of Volozhin, Belarus. The results of this move revolutionised Torah study, and the results of this process are still felt in Orthodox Jewry.

In accordance with the Vilna Gaon's wishes, three groups of his disciples and their families, numbering over 500, made aliyah to the Land of Israel between 1808 and 1812, a movement documented in Arie Morgenstern's book, Hastening Redemption. This immigration is considered to be the beginning of the modern settlement of Israel. These groups of ascetics were called Perushim, meaning "separated", because they separated themselves from worldly pleasures to study the Torah. They originally settled in Safed because the Muslim authorities in Jerusalem prevented settlement by Ashkenazi Jews in that city, but after numerous devastating calamities there, including plague and earthquake, most moved to Jerusalem. Their arrival revived the presence of Ashkenazi Jewry in Jerusalem, which for over 100 years had been mainly Sephardi.

The aliyah of the Perushim had a widespread and ongoing effect on the Jews in Palestine. They spread the teachings of the Vilna Gaon, which had a considerable influence on Jewish thought and religious practice amongst the Ashkenazi community. They also set up several Kollels, founded the Jerusalem neighborhood of Mea Shearim, and were instrumental in rebuilding the Yehudah Hechassid Synagogue (also known as the Hurba Synagogue, or “The Ruins”), which had laid in ruins for 140 years.