Ubaydallah ibn al-Sari () (died 865) was a governor of Egypt from 822 until 826. A son of al-Sari ibn al-Hakam, he was the third and last member of his family to autonomously rule over parts of Egypt during the troubled period following the great Abbasid civil war, and his surrender to Abdallah ibn Tahir in 826 marked the re-imposition of firm Abbasid control over the province for the first time since the outbreak of the conflict.