Who was the first of the kings of Persia to embrace Islam?

The first of the Persian kings to embrace Islam was Ashama ibn Abhar, the Negus (Najashi) king of Abyssinia. He embraced Islam during the time of the Prophet, peace and blessings be upon him, but did not migrate to him. He was beneficial to the Muslims who migrated to him, and the Prophet, peace and blessings be upon him, performed the funeral prayer for him in absentia.