A 9th century astronomer and astrologer. Masha'allah's name is often seen in latinized form as Messahala or Mashallah, and means"what (wonders) Allah has willed". However, it should be noted that some suggest that his name was probably Manasseh, short form Misha.

Masha'allah lived in the caliphate of al-Mansur, and worked with Persian astrologer al-Naubakt in the surveying of land for the building of al-Mansur's new city, Baghdad (named originally Madinat as-Salam, or "City of Peace") and died c. 815 or 820. One of the earliest Islamic astronomers and astrologers, Masha'allah was an Egyptian Jew. His most popular book in the Middle Ages was the De scientia motus orbis, translated into Latin by Gherardo Cremonese in the 12th century, probably from the treatise called in Arabic "the twenty-seventh" (there are no surviving copies of this Arabic treatise).

According to the Cambridge History of English and American Literature, Chaucer's Treatise on the Astrolabe was compiled from Masha'allah and Johannes de Sacrobosco. This assessment is seconded by W.W. Skeat in his magesterial critical edition of that work, but it seems at least possible that Chaucer drew from a similar work by Abu Ma'shar, whose Liber Astronomia was cited frequently in other medieval astrology sources in regard to the making and use of the astrolabe.