In Judaism, shiv'ah or shiva (seven) is the week-long period of grief and mourning for the seven first-degree relatives: father, mother, son, daughter, brother, sister, and spouse. (Grandparents and grandchildren are not included). As most regular activity is interrupted, the process of following the shiv'ah ritual is referred to as sitting shiva. Shiva is part of a suite of customs for bereavement (mourning) in Judaism.

Immediately upon the burial of the departed (which traditionally occurs within one day of death), any first-degree relatives assume the halakhic status of "ovel" (mourner). This state lasts for seven days, during which family members traditionally gather in one home and receive visitors. At the funeral, mourners traditionally make a tear in an outer garment (keriah), which is not mended for the duration of the shiv'ah week. Outside of the Orthodox community, a common alternative is to pin on a small black ribbon which is then torn and worn throughout the period.

It is considered a great mitzvah (good deed commanded by God) of kindness and compassion to pay a home visit to the mourners. Traditionally, no greetings are exchanged and visitors wait for the mourners to initiate conversation. Often, visitors will recite the traditional words of consolation, Ha-Makom y'nachem et'khem b'tokh sh'ar avelei Tziyon viyrushalayim ("May the Omnipresent comfort you among the other mourners of Zion and Jerusalem"). Once engaged in conversation by the mourners, it is appropriate for visitors to talk about the deceased, sharing stories of his or her life. Some mourners use the Shiva as a distraction from their loss, other mourners prefer to openly experience their grief together with friends and family; the visitor just has to be sensitive, let the mourner choose the topic of conversation.

On the first day, it is customary for mourners not to eat their own food. Traditionally, the first meal, which is called the seudat havra'ah (meal of comforting), is supplied by neighbors and friends. The mourners do not bathe or shower for pleasure, do not wear leather shoes and/or jewelry, men do not shave, and in many communities mourners keep any household mirrors covered. The prohibition of bathing includes bathing or showering the whole body, or utilizing hot water. It is permitted to wash separately various parts of the body in cool water. Marital relations and Torah study are not permitted. (It is permitted to study the laws of mourning, as well as that material which may be studied on Tisha B'Av, including Job, Lamentations, portions of Jeremiah and the third chapter of Talmud tractate Moed Katan. No public mourning may occur on Shabbat (the Jewish Sabbath), nor may the burial take place on Shabbat, but the day of Shabbat does count toward the seven-day period. However, "private" mourning restrictions continue during the Sabbath. For example, a mourner may not take a haircut or bathe for pleasure prior to Shabbat, or have marital relations or study Torah (except for reviewing the weekly Torah portion) on Shabbat. It is customary for the mourners to sit on low stools, or even the floor, symbolic of the emotional reality of being "brought low" by the grief. Typically, mourners do not return to work until the end of the week of mourning.

Many communities have an arrangement where members of the chevra kadisha (local Jewish burial society) organise the meals for the mourners, and serve refreshments for visitors. If prayer services are organized in the house of mourning, it is customary for an adult mourner to lead the prayers when capable (in Orthodox communities, this obligation and honor is extended only to adult men).