Muḥammad ibn Zayd ibn Muḥammad ibn Ismā‘il ibn al-Ḥasan ibn Zayd (died 3 October 900), also known as al-Da‘ī al-ṣaghīr ("the Younger Missionary"), is an Alid who succeeds his brother, Hasan ("the Elder Missionary"), as ruler of the Zaydid dynasty of Tabaristan in 884.

Little is known of his early life, before coming to Tabaristan after Hasan establishes Zaydid rule there in 864.

He serves his brother as a general and governor, and continues his policies after his accession.

His reign is troubled by rebellions and wars, most notably by the invasion of Rafi' ibn Harthama in 889–892, which occupies most of his domains.

After Rafi' falls out of favor with the Abbasids, Muhammad recovers his position and secures the allegiance of Rafi', but does not particularly support him against the Saffarids.

In 900, following the Saffarids' defeat by the Samanids, he tries to invade Khurasan, but i defeated and dies of his wounds, whereupon Tabaristan fall sto the Samanids.