Ali Shams al-Din ibn Abdallah (Arabic: علي شمس الدين بن عبدالله, romanized: ʿAlī Shams al-Dīn ibn ʿAbdallāh) was the 18th Tayyibi Isma'ili Dāʿī al-Muṭlaq in Yemen.
[1][2] After the death of Hasan, Ali took up residence in the fortress of Dhu Marmar.
But in 1426, the Zaydi imam of Sana'a, al-Mansur Ali (r. 1391–1436), captured Dhu Marmar after a siege, but allowed the Dāʿī with his family, followers, and possessions to leave the town and move to Haraz, which became the new base of the Tayyibi movement.
[2] The Tayyibis also lost a number of other fortresses to the Zaydis at this time, which were later recovered by Idris Imad al-Din.
This split caused deep anxiety and mental agony to Ali.