The term saris, generally translated to English as “eunuch” or “chamberlain”, appears 45 times in the Tanakh. It frequently refers to a trusted but gender variant person who was delegated authority by a powerful person. It is unclear whether most were in fact castrated. In Isaiah 56 God promises eunuchs who keep the Sabbath and hold fast to his covenant that he will build an especially good monument in heaven for them, to make up for their childlessness.
Some Orthodox assert that sex/gender is an innate and eternal category and cite verses in the Book of Genesis about Adam and Eve and the creation of maleness and femaleness. There are, nevertheless, Orthodox authorities who recognize the medical necessity of sex reassignment as well as the efficacy of sex reassignment surgery (SRS) in changing halachic sex designation. In 2007 Joy Ladin became the first openly transgender professor at an Orthodox institution (Stern College for Women of Yeshiva University).
Conservative Judaism has mixed views on transgender people. In 2003, the CJLS approved a rabbinic ruling that concluded that sex reassignment surgery (SRS) is permissible as a treatment of gender dysphoria, and that a transgender person’s sex status under Jewish law is changed by SRS.[dead link] There have not yet been any openly transgender rabbis or rabbinical students affiliated with Conservative Judaism.
Reform Judaism has expressed positive views on transgender people. Reform Judaism’s Central Conference of American Rabbis first addressed the issue of transgender Jews in 1978, when they deemed it permissible for a person who has undergone sex reassignment surgery (SRS) to be married according to Jewish tradition.  In 1990, the Central Conference of American Rabbis declared that people who have undergone sex reassignment surgery (SRS) may convert to Judaism. In 2002 at the Reform seminary Hebrew Union College-Jewish Institute of Religion in New York, Rabbi Margaret Wenig organized the first school-wide seminar at any rabbinical school which addressed the psychological, legal, and religious issues affecting people who are transsexual or intersex.  In 2003 Reuben Zellman became the first openly transgender person accepted to Hebrew Union College-Jewish Institute of Religion; he was ordained there in 2010. Also in 2003, the Union for Reform Judaism retroactively applied its pro-rights policy on gays and lesbians to the transgender and bisexual communities, issuing a resolution titled, “SUPPORT FOR THE INCLUSION AND ACCEPTANCE OF THE TRANSGENDER AND BISEXUAL COMMUNITIES.”  In 2006 Elliot Kukla, who had come out as transgender six months before his ordination, became the first openly transgender person to be ordained by the Hebrew Union College-Jewish Institute of Religion. In 2007 the Union for Reform Judaism issued a new edition of Kulanu, their resource manual for gay, lesbian, bisexual and transgender inclusion, which for the first time included a blessing sanctifying the sex-change process. It was written by Elliot Kukla at the request of a friend of his who was transgender. Also in 2007, David Saperstein of the Religious Action Center called for a trans-inclusive Employment Non-Discrimination Act.
Reconstructionist Judaism has expressed positive views on transgender people.  In 2003 the Reform rabbi Margaret Wenig organized the first school-wide seminar at the Reconstructionist Rabbinical College which addressed the psychological, legal. and religious issues affecting people who are transsexual or intersex. 
Several non-denominational Jewish groups provide resources for transgender people. Hillel: The Foundation for Jewish Campus Life published an LGBTQ Resource Guide in 2007. Jewish Mosaic has published interpretations of Jewish texts that affirm transgender identities.