Abu Mudhar Ziyadat Allah III (Arabic: أبو مضر زيادة الله الثالث) (died 916) was the eleventh and last Emir of the Aghlabids in Ifriqiya (903–909)
He came to power after the murder of his father Abdullah II in 903. He immediately had all his brothers and uncles executed to eliminate any possible rivals. While this massacre secured his position in the short term, the Aghlabid dynasty lost any remaining prestige it had in the eyes of the people.
The Kutama tribe under Abu 'Abdullah al-Shi'i continued to gain in strength and were able to capture the city of Setif - after two Aghlabid campaigns (905 and 906) ended in failure, ash-Shi'i went on the counter-attack. After the conquest of southern Ifriqiya the troops of the Aghlabids were decisively defeated at al-Aribus on 18 March 909. All of Ifriqiya was now in Kutama hands and the Aghlabid dynasty was ended.
Ziyadat himself managed to escape to the near East, but was unable to secure any help from the Abbasids to regain his emirate. He died in 916 in Palestine.