Kaddish or Qaddish or Qadish (Hebrew: קדיש "holy") is a hymn praising God that is recited during Jewish prayer services. The central theme of the Kaddish is the magnification and sanctification of God's name. In the liturgy, different versions of the Kaddish are functionally chanted or sung as separators of the different sections of the service.

The term Kaddish is often used to refer specifically to "The Mourner's Kaddish," which is chanted as part of the mourning rituals in Judaism in all prayer services, as well as at funerals (other than at the gravesite; see Kaddish acher kevurah "Qaddish after Burial") and memorials; for 11 Hebrew months after the death of a parent; and in some communities for 30 days after the death of a spouse, sibling, or child. When mention is made of "saying Kaddish", this often refers to the rituals of mourning. Mourners recite Kaddish to show that despite the loss they still praise God.

Along with the Shema Yisrael and the Amidah, the Kaddish is one of the most important and central elements in the Jewish liturgy. Kaddish is not, traditionally, recited alone. Along with some other prayers, it traditionally can only be recited with a minyan of ten Jews (a minimum quorum of ten adult Jews).