The Passover Seder (; Hebrew: סדר פסח [ˈseder ˈpesaχ], 'Passover order/arrangement'; Yiddish: סדר [ˈseider]) is a ritual feast at the beginning of the Jewish holiday of Passover. It is conducted throughout the world on the eve of the 15th day of Nisan in the Hebrew calendar (i.e., at the start of the 15th; a Hebrew day begins at sunset). The day falls in late March or in April of the Gregorian calendar; Passover lasts for seven days in Israel and eight days outside Israel. Jews traditionally observe one seder if in Israel and two (one on each of the first two nights) if in the Jewish diaspora. The Seder is a ritual involving a retelling of the story of the liberation of the Israelites from slavery in ancient Egypt, taken from the Book of Exodus (Shemot) in the Jewish Torah. The Seder itself is based on the Biblical verse commanding Jews to retell the story of the Exodus from Egypt: "You shall tell your child on that day, saying, 'It is because of what the LORD did for me when I came out of Egypt.'" (Exodus 13:8) At the seder, Jews read the text of the Haggadah, an ancient Tannaitic work. The Haggadah contains the narrative of the Israelite exodus from Egypt, special blessings and rituals, Talmudic commentaries, and Passover songs.

Seder customs include telling the story, discussing the story, drinking four cups of wine, eating matzah, partaking of symbolic foods, and reclining in celebration of freedom. The Seder is among the most commonly celebrated Jewish rituals, performed by Jews all over the world.