Muhammad bin Ahmad bin Abdullah bin Muhammad bin Yahya bin Muhammad bin Muhammad bin Sayyid al-Nas al-Ya'mari, better known as Abu Bakr Ibn Sayyid al-Nās, was a Medieval Muslim theologian. He was the grandfather of Fatḥ al-Din Ibn Sayyid al-Nās, though he died before ever meeting his grandson.

The Ya'mari were an Arab tribe who settled down in Úbeda in the region of Jaén,^[1] though Ibn Sayyid al-Nas himself was born in Seville^[2] in 1200CE.^[3] The family eventually settled in Tunis due to fighting between Christians and Muslims in Spain, where Ibn Sayyid al-Nas had a son. His grandson, also a Muslim theologian and also called Ibn Sayyid al-Nas, was born in Egypt several years after the death of the elder Ibn Sayyid al-Nas.^[4]

Ibn Sayyid al-Nas studied religion from an early age. He began his education during his early teens under theologians such as Abu al-Abbas al-Nabati, from whom he learned Muslim jurisprudence on the Zahiri rite for over thirty years.^[2] He died in Tunis on June 24, 1261.^[3][5]

Ibn Sayyid al-Nas spent a brief period of time in Aznalcázar before moving to North Africa and accepting positions as the imam of mosques in Tangier and later Béjaïa.^[2] When his reputation spread into Africa, the Hafsid Caliph Muhammad I al-Mustansir invited him to Tunis where he was a favored scholar of the court until his death.^[6] There was a measure of controversy regarding the numerous Ijazah permissions to teach of Ibn Sayyid al-Nas; quite a few of the written permissions were granted by his teacher al-Nabati from al-Nabati's own teachers, whom Ibn Sayyid al-Nas did not meet or study with personally.^[7] Ibn Sayyid al-Nas was said to have memorized over ten thousand hadith, or recorded statements of the Muslim prophet Muhammad, along with their chains of authentication; his students were often awed by his ability to accurately recall all of this from memory.^[7]