Tashlikh or Tashlich (Hebrew: תשליך "cast off") is an customary Jewish atonement ritual performed during the High Holy Days on Rosh Hashanah for Ashkenazi Jews. In some Judaeo-Spanish-speaking communities the practice is referred to as sakudirse las faldas ('to shake the flaps [of clothing]') or simply as faldas.

The ritual is performed at a large, natural body of flowing water (e.g., river, lake, sea, or ocean) on the afternoon of the first day of Rosh Hashanah, the Jewish New Year, although it may be performed until Hoshana Rabbah. If the first day of Rosh Hashanah falls on Shabbat, most Ashkenazim recite Tashlich on the second day of Rosh Hashanah, whereas most Sephardim recite it on the first day as normal. The penitent recites a Biblical passage and, optionally, additional prayers. During the Tashlikh prayer, the worshipers symbolically throw their sins into a source of water. Some people throw small pieces of bread into the water, though many rabbis consider throwing bread into the water on Rosh Hashanah to be forbidden by halakha.

The name "Tashlikh" and the practice itself are derived from an allusion mentioned in the Biblical passage (Micah 7:18–20) recited at the ceremony: "You will cast (tashlikh) all their sins into the depths of the sea."

Most Jewish sources trace the custom back to Yaakov ben Moshe Levi Moelin (d. 1427 in Worms) in his Sefer Maharil, where he explains the custom as a reminder of the binding of Isaac, and the general impression has therefore been that it originated not earlier than the fourteenth century, with the German Jews. Moelin recounts a midrash about that event, according to which Satan threw himself across Abraham's path in the form of a deep stream, in an attempt to prevent Abraham from sacrificing Isaac on Moriah. Abraham and Isaac nevertheless plunged into the river up to their necks and prayed for divine aid, whereupon the river disappeared.

Moelin, however, forbids the practise of throwing pieces of bread to the fish in the river, especially on Shabbat. This would seem to indicate that in his time tashlikh was duly performed, even when the first day of Rosh Hashanah fell on the Sabbath, though in later times the ceremony was, on such occasions, deferred one day.

Rabbi Isaiah Horowitz (born 1555 in Prague — died 1630 in Tiberias) offers the earliest written source explaining the significance of allusions to fish in relation to this custom. In his eponymous treatise, Shelah (214b), he writes:

Rabbi Moses Isserles (Kraków, d. 1572), author of the authoritative Ashkenazi glosses to the Shulchan Aruch, explains:

The deeps of the sea allude to the existence of a single Creator that created the world and that controls the world by, for example, not letting the seas flood the earth. Thus, we go to the sea and reflect upon that on New-Year's Day, the anniversary of Creation. We reflect upon proof of the Creator's creation and of His control, so as to repent of our sins to the Creator, and so he will figuratively "cast our sins into the depths of the sea" (Micah 7:18–20).