Abu ’Ubaida or Ubayda (Ma’mar ibn ul-Muthanna) (728–825) was a Muslim scholar.

Born in Basra, he was a mawla (“client”) of a family from the Arab tribe of Quraish, and “was said, on dubious authority, to have been Jewish.” In his youth, he was a pupil of Abu ’Amr ibn al-’Ala, and in 803 he was called to Baghdad by the Caliph Harun al-Rashid. He died in Basra.

He was one of the most learned and authoritative scholars of his time in all matters pertaining to the Arabic language, antiquities and stories, and is constantly cited by later authors and compilers. Al-Jahiz held him to be the most learned scholar in all branches of human knowledge, and Ibn Hisham accepted his interpretation even of passages in the Qur’an. The titles of 105 of his works are mentioned in the Fihrist of Ibn al-Nadim, and his Book of Days is the basis of parts of the history of Ibn al-Athir and of the Kitab al-Aghani of Abu al-Faraj al-Isfahani, but nothing of his (except a song) seems to exist now in an independent form.