Qājār shah of Iran (1848–96) who began his reign as a reformer but became increasingly conservative, failing to understand the accelerating need for change or for a response to the pressures brought by contact with the Western nations.

Although a younger son of Moḥammad Shāh, Nāṣer od-Dīn was named heir apparent through the influence of his mother. Serious disturbances broke out when he succeeded to the throne on his father's death in 1848, but these were quelled through the efforts of his chief minister, Mīrzā Taqī Khān (Taqī Khān, Mīrzā). Under Taqī Khān's influence, Nāṣer od-Dīn began his rule by instituting a series of needed reforms. Taqī Khān, however, was later forced from power by his enemies, who included Nāṣer od-Dīn's mother, and was disgraced, imprisoned, and finally murdered. In 1852 an attempt was made on Nāṣer od-Dīn's life by two Bābīs (members of a religious sect considered heretical); he responded with a fierce, cruel, and prolonged persecution of the sect.

Unable to regain territory lost to Russia in the early 19th century, Nāṣer od-Dīn sought compensation by seizing Herāt, Afg., in 1856. Great Britain regarded the move as a threat to British India and declared war on Iran, forcing the return of Herāt as well as Iranian recognition of the kingdom of Afghanistan.

Nāṣer od-Dīn was effective in certain areas. He curbed the secular power of the clergy, introduced telegraph and postal services, built roads, opened the first school offering education along Western lines, and launched Iran's first newspaper. He visited Europe in 1873, 1878, and 1889 and was impressed with the technology he saw there. In the later years of his rule, however, he steadfastly refused to deal with the growing pressures for reforms. He also granted a series of concessionary rights to foreigners in return for large payments that went into his own pockets. In 1872 popular pressure forced him to withdraw one concession involving permission to construct such complexes as railways and irrigation works throughout Iran. In 1890 he made an even greater error in granting a 50-year concession on the purchase, sale, and processing of all tobacco in the country, which led to a national boycott of tobacco and the withdrawal of the concession. This last incident is considered by many authorities to be the origin of modern Iranian nationalism. Increasingly unpopular among various Iranian factions, Nāṣer od-Dīn was assassinated in Tehrān by a fanatic.