Mass'oud Mirza Zell-e Soltan (; 5 January 1850 in Tabriz â 2 July 1918 in Isfahan), or Massud Mirza, was an Iranian prince of the Qajar dynasty; he was known as the "Yamin-od-Dowleh" ("Right Hand of the Government"). He was posted as the governor of Isfahan for over 35 years, and the governor of Mazandaran, Fars, and Isfahan for a total of 40 years.
He was the eldest son of Naser al-Din Shah and Effat-od-Dowleh, and the brother of Kamran Mirza Nayeb es-Saltaneh and of Mozaffar ad-Din Mirza (who eventually became Mozaffar ad-Din Shah), but Mas'oud Mirza could not ascend the throne because his mother was not a member of the Qajar dynasty. At the age of thirteen he was appointed the governor of Mazandaran, Turkmen Sahra, Semnan, and Damghan for four years.
He was governor of Isfahan from 1872 to 1907 and governor of Fars from 1907 to 1908. Mass'oud Mirza died in Isfahan in 1918. He was buried in Mashhad. He had 14 sons and 11 daughters.
Zell-e Soltan had 14 sons and 11 daughters including :