Kaddish is a Jewish prayer found in the Siddur praising and sanctifying God's name, and asking for God's kingdom to be established on Earth. It is written in Aramaic, which at the time of the original Kaddish's composition, was the lingua franca of the Jewish people.

A number of versions of the kaddish exist. The Kaddish Shalem, and the Hazi Kaddish are two examples. The most well known form is the "Mourner's Kaddish", said at all prayer services, as well as at funerals and memorials. While all versions of the Kaddish are based on the same words, the chants vary depending on which one. While the Hazi Kaddish has a distinctive upbeat melody, the Mourner's Kaddish is recited slowly and contemplatively in respect for the dead.

Customs for reciting the Mourner's Kaddish vary by synagogue. In reform temples, it is customary that everyone in the synagogue stands to support the mourners. However, in Conservative synagogues, the custom is that only the mourners themselves stand and chant, while the rest of the congregation sits.

Next to the Shema and Amidah, the Kaddish is one of the most important and central blessings in the Jewish prayer service.