| Alauddin Ri'ayat Syah al-Kahar | |
|---|---|
 Grave of al-Kahar in Baitur Rijal (Kandang XII), Banda Aceh | |
| Sultan of Aceh Sultanate | |
| Reign | 1537/1539 – 28 September 1571 |
| Predecessor | Salahuddin of Aceh |
| Successor | Ali Ri'ayat Syah I |
| Born | unknown Banda Aceh, Aceh Sultanate (now Indonesia) |
| Died | 28 September 1571 Banda Aceh, Aceh Sultanate, (now Indonesia) |
| Burial | Cemetery Complex of the Sultans of Aceh Kandang XII, Banda Aceh |
| Spouse | unknown |
| Issue | Abdullah Husain Sri Alam Abdul Jalil |
| Father | Ali Mughayat Syah |
| Mother | unnamed daughter of Inayat Syah |
Alauddin Ri'ayat Syah al-Kahar (died 29 September 1571) was the third Sultan of the Aceh Sultanate, reigning from either 1537 or 1539 until his death. He is considered to be one of the strongest rulers in the history of the sultanate and greatly strengthened Aceh. Alauddin's reign was marked by increased conflict with his Portuguese and Malay rivals and his dispatching of envoys to the Ottoman sultan, Suleiman the Magnificent in the 1560s.