The siege of Herat took place in late 1833 at Herat between Qajar Iran and the city's local Durrani ruler, Kamran Shah Durrani.

Herat, a frontier vassalage barely under Iranian control, was seen by the Qajar dynasty as an integral part of the Guarded Domains of Iran. Due to widespread anti-Iranian tensions in Herat and Britain's increasing engagement in Afghanistan, Iran's rule over Herat was under heavy threat. The British East India Company had started to advocate for Herat's autonomy as a buffer state between northwestern India, Russia and Iran, even though they had previously supported Iranian rule over the city.

In late 1831, the Iranian crown prince Abbas Mirza received the governorship of Khorasan, which amongst other things led to growing hostilities with Kamran Shah Durrani, the Durrani ruler of Herat. The latter received an ultimatum from Abbas Mirza at the beginning of 1833 with two options: either have the name of the Iranian shah (king) mentioned on coin engravings and Friday prayers, pay taxes, and release hostages, or relinquish Herat and appear at the Iranian court.

Kamran Shah responded by offering a "gift" of 15,000 toman in gold coins, cautioning Abbas Mirza to prepare for war if he wanted more. In the summer of 1833, Abbas Mirza sent an army to besiege Herat. Abbas Mirza wanted to capture to Herat to both show his military capabilities and to advance the eastern objectives of the Russian Empire, following diplomatic directives from the court in Tehran. Iran's control of Herat was seen by the Russians as a threat to British India and a challenge to British objectives in Afghanistan. The Iranian army against Herat was led by Abbas Mirza's sons Mohammad Mirza and Khosrow Mirza, as well as his minister Abol-Qasem Qa'em-Maqam.

As a result, Kamran Shah made an alliance with the British, whose operatives convinced him to oppose a military takeover by Iran. Capturing a portion of Iranian territory in Sistan was something he also considered. Mohammad Mirza was forced to end the siege and return to Tehran after learning of Abbas Mirza's death in Mashhad in November 1833. There, he was crowned the new crown prince. In late November 1833, Mohammad Mirza summoned the vizier of Herat, Yar Muhammad Khan Alakozai, to Mashhad and put him in charge of negotiating a deal with Herat. A treaty was shortly made afterwards, in which Kamran Shah was required to send one of his sons as a hostage, have the name of the Iranian shah mentioned on coin engravings and Friday prayers, and provide 15,000 toman and 50 rolls of cashmere wool as a "gift".

Even though Herat was officially under Iranian control due to the Iranian shah being mentioned on coin engravings and Friday prayers, the income generated from there had significantly decreased compared to 1817 and was insignificant when compared to the income generated by the provinces that were more well-established in Iran.

• Amanat, Abbas (2003). "Herat vi. The Herat question". In Yarshater, Ehsan (ed.). Encyclopædia Iranica, Volume XII/2: Hedāyat al-mota'allemin–Herat VII. London and New York: Routledge & Kegan Paul. pp. 219–224. ISBN 978-0-933273-75-7.
• Noelle-Karimi, Christine (2014). The Pearl in its Midst: Herat and the Mapping of Khurasan (15th-19th Centuries). Wien: Austrian Academy of Sciences. ISBN 9783700172024. OCLC 879441128.