Hanukkah (/ˈhænəkə/, /ˈhɑːnəkə/; חֲנֻכָּה‎ Ḥănukkā listen^ⓘ) is a Rabbinic Jewish festival commemorating the recovery of Jerusalem and subsequent rededication of the Second Temple at the beginning of the Maccabean Revolt against the Seleucid Empire in the 2nd century BCE.

Hanukkah is observed for eight nights and days, starting on the 25th day of Kislev according to the Hebrew calendar, which may occur at any time from November 28 to December 27 in the Gregorian calendar. The festival is observed by lighting the candles of a candelabrum with nine branches, commonly called a menorah or hanukkiah. One branch is placed above or below the others and its candle is used to light the other eight candles. This unique candle is called the shammash (שַׁמָּשׁ‎, "attendant"). Each night, one additional candle is lit by the shammash until all eight candles are lit together on the final night of the festival.

Other Hanukkah festivities include singing Hanukkah songs, playing the game of dreidel and eating oil-based foods, such as latkes and sufganiyot (similar to jelly donuts), and dairy foods. Since the 1970s, the worldwide Chabad Hasidic movement has initiated public menorah lightings in open public places in many countries.

Originally instituted as a feast "in the manner of Sukkot (Booths)", it does not come with the corresponding obligations, and is therefore a relatively minor holiday in strictly religious terms. Nevertheless, Hanukkah has attained major cultural significance in North America and elsewhere, especially among secular Jews, due to often occurring around the same time as Christmas during the festive season.

The name "Hanukkah" derives from the Hebrew verb "חנך‎", meaning "to dedicate", because on Hanukkah, the Maccabean Jews regained control of Jerusalem and rededicated the Temple.

Many homiletical explanations have been given for the name:

In Hebrew, the word Hanukkah is written חֲנֻכָּה‎ or חֲנוּכָּה‎ (Ḥănukā). It is most commonly transliterated to English as Hanukkah or Chanukah. The spelling Hanukkah, which is based on using characters of the English alphabet as symbols to re-create the word's correct spelling in Hebrew, is the most common and the preferred choice of Merriam–Webster, Collins English Dictionary, the Oxford Style Manual, and the style guides of The New York Times and The Guardian. The sound represented by Ch ([χ], similar to the Scottish pronunciation of loch) is not native to the English language, so those not familiar with Hebrew pronunciation may pronounce it with an h ([h]). Furthermore, the letter ḥeth (ח‎), which is the first letter in the Hebrew spelling, is pronounced differently in modern Hebrew (voiceless uvular fricative) from in classical Hebrew (voiceless pharyngeal fricative [ħ]), and neither of those sounds is unambiguously representable in English spelling. However, its original sound is closer to the English H than to the Scottish Ch, and Hanukkah more accurately represents the spelling in the Hebrew alphabet. Moreover, the 'kaf' consonant is geminate in classical (but not modern) Hebrew. Adapting the classical Hebrew pronunciation with the geminate and pharyngeal Ḥeth can lead to the spelling Hanukkah, while adapting the modern Hebrew pronunciation with no gemination and uvular Ḥeth leads to the spelling Chanukah.

In Modern Hebrew, Hanukkah may also be called the Festival of Lights (חַג הַאוּרִים‎, Ḥag HaUrim), based on a comment by Josephus in Antiquities of the Jews, καὶ ἐξ ἐκείνου μέχρι τοῦ δεῦρο τὴν ἑορτὴν ἄγομεν καλοῦντες αὐτὴν φῶτα "And from then on we celebrate this festival, and we call it Lights". The first Hebrew translation of Antiquities (1864) used (חַג הַמְּאֹרוֹת‎) "Festival of Lamps", but the translation "Festival of Lights" (חַג הַאוּרִים‎) appeared by the end of the nineteenth century.