The machzor is the prayer book which is used by Jews on the High Holy Days of Rosh Hashanah and Yom Kippur. Many Jews also make use of specialized machzorim on the three pilgrimage festivals of Passover, Shavuot, and Sukkot. The machzor is a specialized form of the siddur, which is generally intended for use in weekday and Shabbat services.

Rosh HaShanah is the New Year in Judaism. The biblical name for this holiday is Yom Teruah. It is the first of the High Holy Days, as specified by Leviticus 23:23–25, that occur in the late summer/early autumn of the Northern Hemisphere. Rosh Hashanah begins ten days of penitence culminating in Yom Kippur, as well as beginning the cycle of autumnal religious festivals running through Sukkot which end on Shemini Atzeret in Israel and Simchat Torah everywhere else.