When a Jewish child reaches the age of maturity (12 years and one day for girls, 13 years and one day for boys) that child becomes responsible for him/herself under Jewish law; at this point a boy is said to become Bar Mitzvah (בר מצווה, "son of the commandment"); a girl is said to become Bat Mitzvah (בת מצווה, "daughter of the commandment"). The collective term for Bar and Bat Mitzvot is B'nai Mitzvah.

Before this age, all responsibility lies with the parents. After this age, the children are privileged to participate in all areas of Jewish community life and bear their own responsibility in the areas of Jewish ritual law, tradition, and ethics.

Since medieval times it was traditional for a boy to celebrate becoming Bar Mitzvah. On the Shabbat after his 13th birthday, he may read from the Torah and Haftara, give a d'var Torah (homily), and/or lead part of the prayer services. This is often followed by a celebratory meal with family, friends, and members of the community.

Except in Italy, no similar ceremony evolved at that time for Jewish girls. This is because women were not considered obliged to obey the same laws as men. Since there was no obligation for them as adults, there was no issue of change in a girl's status.

However, in the 19th and 20th centuries, Jews of the Reform, Conservative, and Reconstructionist denominations reconceived the notion of "obligation" and gender distinctions within Judaism. Today, non-orthodox Jews celebrate a girl's becoming Bat Mitzvah in the same way as a boy's becoming Bar Mitzvah. Most Reform and Conservative synagogues have egalitarian participation in which women may read from the Torah and lead services. Conservative Judaism is pluralistic, and some synagogues are still concerned about the halakhic propriety of women reading the Torah portion to men. (Some believe that a woman's voice distracts men from fulfilling their obligation in a pious spirit.) In such congregations girls read from the Haftara. Reform Judaism is entirely egalitarian. The majority of Orthodox Judaism rejects the idea that a woman can read from the Torah or lead prayer services and has developed a less public way to mark this occasion.