Hallel (Hebrew: הַלֵּל, 'Praise') is a Jewish prayer, a verbatim recitation from Psalms 113–118 which is recited by observant Jews on Jewish holidays as an act of praise and thanksgiving.

Full Hallel (Hebrew: הלל שלם, romanized: Hallel shalem, lit. 'complete Hallel') consists of all six Psalms of the Hallel, in their entirety. It is a Jewish prayer recited on the first two nights and days of Pesach (only the first night and day in Israel), on Shavuot, all seven days of Sukkot, on Shemini Atzeret and Simchat Torah, and on the eight days of Hanukkah. The sages have provided a "siman" (a way to remember) the days when full Hallel is recited. It is called "BeBeTaCh".

A blessing is recited at the beginning and end of Full Hallel.

Partial Hallel (Hebrew: חצי הלל, romanized: chatzi Hallel, lit. 'half Hallel') omits parts of the Full Hallel: The first 11 verses of both Psalms 115 and 116 are omitted. In Yemenite Jewish custom, additional passages are omitted: Psalm 117, and Psalm 118:1–4.

Partial Hallel is recited on the last six days of Pesach and on Rosh Chodesh. On these days Hallel was originally not recited at all, and the partial recitation indicates that it is only done by later custom rather than to fulfill a requirement. Regarding Passover, the Talmud argues that Full Hallel is only recited on days when the Temple sacrifice differed from the previous day's, while the sacrifice for all days of Passover was identical. Other sources suggest a different reason: that Full Hallel is omitted on the seventh day of Passover in consideration of the Egyptians who died during the Crossing the Red Sea, and omitted on the middle days of Passover so that they not overshadow the seventh day. Regarding Rosh Chodesh, the Talmud states that Hallel is only required on days on which work is forbidden, which is not the case on Rosh Chodesh.

While Ashkenazi Jews recite a blessing at the beginning and end of Partial Hallel, some Sephardic Jews do not, and the few Sephardic communities that do recite a blessing on half Hallel (Moroccans and Spanish & Portuguese Jews, as well as some others) recite likro et hahallel (to read the Hallel, as is always recited by contemporary Ashkenazim) on Half Hallel, as opposed to the blessing ligmor et hahallel (to complete the Hallel) that they recite on Full Hallel.

Hallel consists of six Psalms (113–118), which are recited as a unit, on joyous occasions including the each day of the Three Pilgrimage Festivals (Passover, Shavuot, and Sukkot), as well as at Hanukkah and Rosh Chodesh.

On all these occasions, Hallel is recited as part of the morning Shacharit prayer service, following the Amidah. In addition, it is recited in many communities during the evening prayers on the first (and, outside Israel, second) night of Pesach; however, according to the original Nusach Ashkenaz it is not recited at this time, and thus it is not recited in communities such as Litvaks (although most Litvish communities in Israel do recite it) and Yekkes. It is recited in all communities during the Passover Seder service. According to the Talmud, there was a dispute between the Houses of Hillel and Shammai regarding the reading of Hallel during the Seder. According to the school of Shammai, only the first psalm (Ps. 113) should be read before the meal, whereas the school of Hillel advocated reading the first two psalms (Ps. 113 and 114). The remaining Psalms would be said after the Grace After Meals (as is usually the case, the halacha follows the school of Hillel).