A Jewish holiday or festival is a day or series of days observed by Jews as a holy or secular commemoration of an important event in Jewish history. In Hebrew, Jewish holidays and festivals, depending on their nature, may be called yom tov ("good day") (Yiddish: yontif) or chag ("festival") or ta'anit ("fast").

The origins of various Jewish holidays generally can be found in Biblical mitzvot (commandments), rabbinical mandate, and modern Israeli history.