The duration of the longevity of Imam Mahdi’s life has been an area of disagreement among several Sunni and Shi‘i scholars. The findings of this research are based on the Qur’anic verses, Shi‘a and Sunni hadith, biological and medical law, and historical documents. These findings reveal that it is possible to live an exceedingly long life, as the Prophet Noah, the Men of the Cave, and Prophet Khidr are among those who have done so. Longevity, with its conditions, is also possible according to biological and medical law, and history has witnessed those who were not prophets who have lived prolonged lives. Moreover, the longevity of Imam Mahdi is not considered unnatural and opposed to the Holy Qur’an and hadith.