Shammai was a Jewish scholar of the first century BCE, and an imporant figure in Judaism's core work of rabbinic literature, the Mishnah.

Shammai was the most eminent contemporary and the halakic opponent of Hillel, and is almost invariably mentioned along with him.

After Menahem the Essene had resigned the office of vice-president of the Sanhedrin, Shammai was elected to it, Hillel being at the time president. Shammai was likely a Palestinian Jew, and took an active part in the political and religious complications of his native land. Of an irascible temperament, he seemed to lack some of the tireless patience which is said to have distinguished Hillel. Once, when a gentile came to him and asked to be converted to Judaism upon conditions which Shammai held to be impossible, he drove the applicant away; whereas Hillel succeeded in converting him (Talmud, tracate Shabbat 31a).

Nevertheless Shammai was in no wise a misanthrope. He himself appears to have realized the disadvantages of his temper; hence he recommended a friendly attitude toward all. His motto was: "Make the study of the Torah your chief occupation; speak little, but accomplish much; and receive every man with a friendly countenance" (Ab. i. 15). He was modest even toward his pupils.

In his religious views Shammai was known to be strict. He wished to make his son, while still a child, conform to the law regarding fasting on Yom Kippur, the Day of Atonement; he was dissuaded from his purpose only through the insistence of his friends (Talmud, Yoma 77b). Once, when his daughter-in-law gave birth to a boy on Sukkot (the Feast of Tabernacles) he broke through the roof of the chamber in which she lay in order to make a sukkah of it, so that his new-born grandchild might fulfil the religious obligation of the festival (Talmud Sukkot 28a).

In the Midrash Sifre, Deut. § 203 it is said that Shammai commented exegetically upon three passages of Scripture. These three examples of his exegesis are: (1) the interpretation of Deut. xx. 20 (Tosef., 'Er. iii. 7); (2) that of II Sam. xii. 9 (Ḳid. 43a); and (3) either the interpretation of Lev. xi. 34, which is given anonymously in Sifra on the passage, but which is the basis for Shammai's halakah transmitted in 'Orlah ii. 5, or else the interpretation of Ex. xx. 8 ("Remember the Sabbath"), which is given in the Mekilta, Yitro, 7 (ed. Weiss, p. 76b) in the name of Eleazar b. Hananiah, but which must have originated with Shammai, with whose custom of preparing for the Sabbath it accords.

Shammai founded a school of his own, which differed fundamentally from that of Hillel; and many of Shammai's sayings are probably embodied in those handed down in the name of his school.

See also: Mishnah