who is imam mahdi?

Muhammad al-Mahdi
Imam
Muhammad ibn Hasan al-Mahdī is believed by Twelver Shī‘a Muslims to be the Mahdī, an ultimate savior of humankind and the final Imām of the Twelve Imams who will emerge with Isa(jesus) in order to fulfill the mission of his forefathers.
 
Born: July 29, 869 AD, Samarra, Iraq
Full name: Muhammad ibn Hasan al-Mahdī
Parents: Narjis, Hasan al-Askari
Grandparents: Ali al-Hadi, Hâdise
Great-grandparents: Muhammad al-Jawad, Lady Sumānah
Agent: Uthman ibn Sa’id al-Asadi, Abul Qasim Husayn ibn Ruh al-Nawbakhti