Bahá'u'lláh became a follower of the Báb in Persia in 1845. Three years after the Báb was executed, he was exiled to Baghdad (then a part of the Ottoman Empire), where in 1863 he proclaimed the Bahá'í Faith when he declared himself He whom God shall make manifest, a messianic figure in Babi theology. Bahá'u'lláh based this announcement on a vision of the Maid of Heaven he claimed to have had while imprisoned in the Síyáh-Chál in Tehran, Persia. He would be further exiled to Edirne and ultimately to the prison city of Acre, Palestine (present-day Israel), where he died. He wrote many religious works, most notably the Kitáb-i-Aqdas, the Kitáb-i-Íqán, and the Hidden Words.
Bahá'u'lláh's teachings focus on the unity of God, religion, and mankind. Similar to other monotheistic religions, God is considered the source of all created things. Religion, according to Bahá'u'lláh, is renewed periodically by Manifestations of God, people who are made perfect through divine intervention and whose teachings are the sources of the major world religions throughout history. Bahá'ís view Bahá'u'lláh as the first of these teachers whose mission includes the spiritual unification of the entire planet through the eradication of racism and nationalism. Bahá'u'lláh's teachings include the need for a world tribunal to adjudicate disputes between nations, a uniform system of weights and measures, and an auxiliary language that could be spoken by all the people on earth. Bahá'u'lláh also taught that the cycles of revelatory renewal will continue in the future, with Manifestations of God appearing every thousand years or so.
Bahá'u'lláh's eldest son, `Abdu'l-Bahá, was appointed his successor.
Bahá'u'lláh was born on 12 November 1817, in Tehran, the capital of Persia, present-day Iran. Bahá'í authors state that his ancestry can be traced back to Abraham through Abraham's wife Keturah, to Zoroaster and to Yazdgerd III, the last king of the Sassanid Empire, and also to Jesse. According to the Bahá'í author John Able, Bahá'ís also consider Bahá'u'lláh to have been "descended doubly, from both Abraham and Sarah, and separately from Abraham and Keturah." His mother was Khadíjih Khánum and his father was Mírzá Buzurg. Bahá'u'lláh's father served as vizier to Imám-Virdi Mírzá, the twelfth son of Fat′h Ali Shah Qajar. Mírzá Buzurg was later appointed governor of Burujird and Lorestan, a position that he was stripped of during a government purge when Muhammad Shah came to power. After the death of his father, Bahá'u'lláh was asked to take a government post by the new vizier Hajji Mirza Aqasi, but declined.
Bahá'u'lláh had three wives. He married his first wife Ásíyih Khánum, the daughter of a nobleman, in Tehran in 1835, when he was 18 and she was 15. She was given the title of The Most Exalted Leaf and Navváb. His second wife was his widowed cousin Fátimih Khánum. The marriage took place in Tehran in 1849 when she was 21 and he was 32. She was known as Mahd-i-`Ulyá. His third wife was Gawhar Khánum and the marriage occurred in Baghdad sometime before 1863.