Which tractate of the Talmud discusses the laws of Rosh Hashanah?

The Talmudic tractate that discusses the laws of Rosh Hashanah is tractate Rosh Hashanah.

Rosh Hashanah is a tractate of the Mishnah that also forms the basis of corresponding discussions in both the Babylonian Talmud and the Jerusalem Talmud. Its subjects extend beyond the holiday itself. The tractate explains how the ancient Jewish court established the new month from eyewitness testimony about the moon, how messengers announced the decision, and how the calendar was coordinated across distant communities.

It also discusses the shofar: which horns may be used, how the instrument is sounded, and when the obligation applies. Its final chapter covers the order of the Rosh Hashanah prayers, including the sections known as Malkhuyot, Zikhronot, and Shofarot.

A frequent mix-up is confusing a tractate with a biblical book or a festival name. The title Rosh Hashanah refers both to the Jewish New Year observance and to this rabbinic legal-literary work. In the Mishnah’s traditional arrangement, the tractate belongs to Seder Moed, the order devoted chiefly to appointed times, Sabbaths, and festivals.