Abū Muḥammad al-Ḥasan ibn Zayd ibn Muḥammad ibn Ismaʿīl ibn al-Ḥasan ibn Zayd (Arabic: الحسن بن زيد بن محمد; died 6 January 884), also known as al-Dāʿī al-Kabīr (Arabic: الداعي الكبير, "the Great/Elder Missionary"), was an Alid who became the founder of the Zaydid dynasty of Tabaristan.