Mohammad Shah Qajar (Persian: محمدشاهقاجار; English: Mohammad Shah Qajar; January 5, 1808- September 5, 1848) was the Persian king of the Qajar dynasty.

Mohammed Shah was the grandson of the second Shah of the dynasty, Shah Fath Ali Shah Qajar, and the son of Abbas Mirza. Abbas Mirza was originally a crown prince, but his death made Mohammed Shah a crown prince. After the death of Fateh Ali Shah, one of his sons, Ali Mirza, attempted to compete for the throne. Ali Mirza was deposed by Ghaem Magham Farahani after 40 days of reign.

Politics and Military
After ascending to the throne, Muhammad Shah forgave Ali Mirza and appointed Farahani as prime minister to thank him for his help. However, in 1835, Shah was instigated by his minister Hajj Mirza Aghasi to order the execution of Farahani, and Shah's policies were largely influenced by Aghasi. One of Agassi's wives, Malek Jahan Khanom (a princess of the Qajar dynasty and cousin of Mohammed Shah), later remarried Mohammed Shah. Her son, Nasreddin Shah, later became Shah, and Nasreddin Shah was influenced by her.
Mohammed Shah attempted twice to capture Herat under British protection, and the Siege of Herat from 1837 to 1838 ended in failure. Mohammed Shah sent officials to King Louis Philippe I of France for this purpose. In 1839, two French military instructors arrived in Tabriz to assist him, but the French also failed to help him capture Herat.
Mohammed Shah was weak and sickly, and he died of gout at the age of 40.
Cultural Trends
Shah is influenced by Russia and is attempting modernization reforms to strengthen ties with the West. His successor, Nasir Din Shah, also adopted this route. Nasir Din Shah was a skilled ruler. The modernization efforts have brought photography to this country, and a large number of small-scale lacquer oil paintings have emerged.
During the reign of Mohammed Shah, the Bab religious movement was prevalent. The Persian lion and sun, as well as the red, white, and green background colors, became the national flag during this period.