Bahá'u'lláh (Hossein Ali Nouri) was born in Tehran on 12 November 1817 into the household of a prominent Iranian government official, Mirza Abbas Nouri, known as Mirza Bozorg, who served at first as minister to one of the sons of Fath-`Ali Shah (r. 1797-1834), and then, late in the same shah's reign, he was appointed governor of Boroujerd and Lorestan. Mirza Bozorg was in the circle of Mirza Abu'l-Qasem, the Qa'em-Maqam who was then grand vizier.
After the death of Fath-'Ali Shah in 1834, his son Mohammad Shah (r. 1834-1848) came to power. The young king wanted to establish his own authority, and he had the grand vizier, Qa'em-Maqam, disgraced and killed. Bahá'u'lláh's father, Mirza Bozorg, was stripped of his office and government salary but he retained the Nouri family's ancestral estates around the village of Takour in the Nour district of Mazandaran province.
Although Mirza Bozorg was out of favour at court, the new grand vizier, Haji Mirza Aqasi, offered the young Bahá'u'lláh a government post, which the latter declined. Bahá'u'lláh in his youth showed himself a sensitive and spiritual young man; he came into contact with believers in the mystical, obscure school of Sheikhis in Nour.
In 1844, Mulla Hossein Boshrou'i arrived in Tehran in order to spread the Babi faith among the Sheikhi communities, convey the Bab's message to Bahá'u'lláh. Young Bahá'u'lláh accepted the new religion eagerly. Later when he returned to Takour from Tehran, spent lots of efforts in spreading the Babi faith in Nour and Mazandaran. Because of the prominence of his family, and his own charismatic personality, Bahá'u'lláh's first teaching efforts yielded some new believers, including some members of the Shi`ite clergy. Bahá'u'lláh also taught the faith to his brothers, including Mirza Musa and Mirza Yahya. Bahá'u'lláh also attempted to use his influence to protect other Babis, and he supported Tahereh Qurrat u'l-`Ayn and some other Babis when she was accused of complicity in the killing of her uncle, Mulla Taqi Baraghani. As a consequence of his coming out into the open, Bahá'u'lláh was briefly imprisoned in Tehran.
In the summer of 1848, eighty-one prominent Babis gathered at the village of Badasht in northwestern Iran to discuss ways of freeing the Bab from his imprisonment in Azerbaijan. Bahá'u'lláh attended with his brothers, but largely stayed in the background. He suggested divine names for some of the Babis, in accordance with the Bab's instructions that his followers glorify God in this manner, and it was at this point that he adopted for himself the name Baha', or the divine glory. His young brother, Mirza Yahya, then 17, became Sobh-e Azal or the Morn of Eternity. A conflict broke out at Badasht among Babis who wished to proclaim the abrogation of Islamic law and the establishment of the Bab's independent revelation, and those who saw the Babi religion as still compatible with preservation of Shi`a legal codes. Bahá'u'lláh, like Qurrat u'l-`Ayn, supported the adoption of the new revealed law of the Bab, which was a winning position.
In the upheavals and persecutions of the late 1840s, Bab had lost many of his major disciples. He began increasingly corresponding with other followers, including Bahá'u'lláh, and Mulla `Ali "`Azim" Turshizi and Azal as well. It is said that in the winter of 1850, Bahá'u'lláh was corresponding with the Bab, dictating his letters to Mirza Yahya; for the purposes of secrecy, these letters were sent in Mirza Yahya's name. It is widely believed that some of the letters the Bab wrote to Mirza Yahya in this period actually appear to have been addressed through him to Bahá'u'lláh. By the spring of 1850 the grand vizier, Amir Kabir, was putting great pressure on the Babis, and the religion needed a secret head whose identity remained unknown to the authorities. Bahá'u'lláh and Mulla `Abdu'l-Karim decided to give it out that Mirza Yahya Azal was the chief of the new religion, in order to protect Bahá'u'lláh, now the real leader of the underground Babis. Many prominent Babis acknowledged Mirza Yahya Azal as a "Mirror"; but there is no evidence that the Bab appointed him as a successor, and there were many Mirrors among the Bab's followers.
The Iranian government in July 1850 executed the Bab. Thereafter a number of important Babis put forth claims, including, in 1851, Sayyid Basir-e Hindi Multani. Bahá'u'lláh challenged him, and claimed his own divinity. In June 1851, the grand vizier, Amir Kabir, put pressure on Bahá'u'lláh to leave the country, which was clear who the Babi community's leader was. Consequently, Bahá'u'lláh went to the holy city of Karbala in Iraq, the site of Imam Hossein's shrine, where a small Babi group existed. Bahá'u'lláh, during his stay in Karbala between August 1851 and March 1852, told some of his close companions that he was himself the return of the Imam Hossein, whose return Shi`ites expected after the advent of the Qa'em or Mahdi.
During Bahá'u'lláh's absence, the more radical leaders of the Babi community in Tehran, such as Azim and Azal, plotted the assassination of Naser od-Din Shah in retaliation for his execution of the Bab. In the meantime, a new grand vizier had come to power, Mirza Aqa Khan Nouri, a cousin of Bahá'u'lláh, and he called Bahá'u'lláh back to the capital. There was some expectation of better relations between the government and the Babis. On his arrival, however, Bahá'u'lláh discovered the assassination plot, and denounced it. The plot was carried out on August 15, 1852, by some Babi fanatics, but failed when the pistol misfired. Meanwhile, Bahá'u'lláh was staying with his brother-in-law, a secretary to the Russian ambassador. The shah demanded that the Russian embassy allow Bahá'u'lláh to be surrendered to the government, but they handed him over to the grand vizier, Aqa Khan Nouri, who was sympathetic to him. Aqa Khan Nouri found it impossible to protect Bahá'u'lláh when anti-Babi riots broke out in Tehran, and Bahá'u'lláh was arrested, chained and sent to the Siyah-Chal, the Black Pit dungeon. During his imprisonment, Bahá'u'lláh saw suffering and execution of many of his Babi friends, which encouraged him to commit to reform the Babi community.
Bahá'u'lláh was found innocent of complicity in the assassination plot. The government gave him permission to go to Baghdad, in Ottoman Iraq, where he arrived on 12 January 1853. Later in 1854 Bahá'u'lláh secretly departed from Baghdad, taking with him only one companion and went to Kurdistan in the north where he for some time. While in Kurdistan Bahá'u'lláh wrote his "Ode of the Nightingale," an Arabic poem in classical Sufi style that mentions his "mission" for the first time. Bahá'u'lláh, with his good contacts with the Kurds, attempted to widen the base of the Babi movement away from Iranian Shi`ites by attracting the Sunni, Sufi, Kurds into his faith.
In 1856 by the request of Babi community as they lacked firm leadership, Bahá'u'lláh returned to Baghdad. In the late 1850s Bahá'u'lláh wrote important works such as The Hidden Words and Seven Valleys, which encouraged some Babis back in Iran.
Bahá'u'lláh in his Book of Certitude, 1861-62, made no open claim as the promised one of the Bab; but he have been waiting for the year 1280 of lunar Islamic calendar (1863-64) to make more open declaration, since some Muslims expected that a messiah would arise in that year. In the spring of 1863 Bahá'u'lláh was ordered to travel to Istanbul as Ottoman Sultan `Abdu'l-`Aziz wanted him brought to the capital. Before leaving, Bahá'u'lláh informed a select handful of close followers and relatives that he was the promised one of the Bab, he claimed "He whom God shall make manifest." Later in Istanbul Ottoman government, under the Iranian ambassador's pressure, ordered that Bahá'u'lláh be exiled to Edirne, where he lived from 1863 to 1868. Bahá'u'lláh and his household received allowances from the Ottoman government. Between 1866 and 1868 Bahá'u'lláh wrote his Epistles to the Rulers, addressing Ottoman Sultan `Abdu'l-`Aziz, Naser od-Din Shah of Iran, and Napoleon III of France.
Bahá'u'lláh claim, "He whom God shall make manifest", vitally threatened the position of Azal, then widely recognized in Iran as the head of the religion, resulted in an open conflict between two brothers. They approached Ottoman government with complaints, which consequently resulted in an investigation into the Babis at Edirne. The commission concluded that Bahá'u'lláh's new claim and propagation pose a possible source of turmoil. The sultan therefore ordered that Bahá'u'lláh and some of his companions be exiled to fortress-prison of Akka on the Syrian coast; but Azal and his followers were sent to Cyprus.
Bahá'u'lláh continued his proclamation to the rulers of the major powers, writing Queen Victoria of Britain, Tsar Alexander II of Russia, Kaiser Wilhelm I of Prussia, and Pope Pius IX. In these letters he announced himself the promised one of all religions. Bahá'u'lláh's more open proclamation in 1866-67, met with widespread acceptance among the Babis back in Iran, the vast majority of whom now became Bahá'ís.
In 1873 Bahá'u'lláh authored his most important work, "Ketab-e Aqdas" (the Most Holy Book), the book of laws for the Bahá'í religion, intended to abrogate for Bahá'ís the canon law of both the Babi faith and of Islam. Bahá'u'lláh had by 1873 already been permitted to move out of the Akka prison, and to rent a residence in the town. In 1877, the local Ottoman governor gave him permission to live in a mansion outside Akka, at Mazra`a. In 1879 he moved to another mansion, at Bahji (literally the "small garden," Bagche, in Turkish), where he lived until his death.
Bahá'u'lláh married three times, first Asiyeh "Nuvvab" Khanom in his youth, then his cousin, Mahd-e `Ulya, whose family had been killed in prosecution of the Babis in Iran; he had a number of children with each of these co-wives. In Baghdad he married Gawhar Khanom, which appears to have been temporary marriage (mut`ah) of Shi`ite law, and Gawhar Khanom was to serve Asiyeh Khanom. Bahá'u'lláh had only one child, a daughter, with Gawhar Khanom. He had altogether fourteen children from his three wives, including four daughters. Five of his sons predeceased him. Bahá'u'lláh appointed his eldest son, `Abdu'l-Bahá, as his successor and the official interpreter of his religion after his death. At the age of 74, he died of a fever in `Akka on 29 May 1892.