Abū 'l-Ḥasan al-Muḫtār Yuwānnīs ibn al-Ḥasan ibn ʿAbdūn ibn Saʿdūn ibn Buṭlān (Arabic: أبو الحسن المختار إيوانيس بن الحسن بن عبدون بن سعدون بن بطلان ; c. 1001 to 1025 – 8 Šauwāl 458 AH or 2 September 1066), commonly known as Ibn Buṭlān (ابن بطلان ), was an Arab physician and Nestorian Christian theologian. Born in Baghdad, the erstwhile capital city of the Abbasid Caliphate, he travelled throughout Mesopotamia, Syria, Egypt, and Anatolia, during which time he practiced medicine, studied, wrote, and engaged in intellectual debates—most famously the Battle of the Physicians with the Egyptian polymath Ibn Riḍwān. In 1054, he was in Constantinople, the capital city of the Byzantine Empire, where he witnessed first-hand the East–West Schism among Christendom, contributing a work to the discussions surrounding it for Michael I Cerularius, who was serving as the Patriarch of Constantinople. After his time in Constantinople, Ibn Buṭlān remained in the Byzantine Empire and eventually became a monk for the Greek Orthodox Patriarchate of Antioch amidst the end of the Macedonian Renaissance.
He is most renowned for his work Taqwīm aṣ-Ṣiḥḥa (تقويم الصحّة , lit. 'Tabular Register of Health'), a handbook on dietetics and hygiene. It was named for its intricate tables, similar to those found within a Taqwīm as-Sana (تقويم السنة, lit. 'tabular register of the year'), a type of astrological almanac. He was the first person to use these tables in a non-astrological work, creating a new scientific writing format that may be seen as the main influence for works like Taqwīm al-Abdān fī Tadbīr al-Insān by the Arab physician Ibn Ǧazla and Taqwīm al-Buldān by the Kurdish geographer and historian Abū 'l-Fidāʾ. Translations of Taqwīm aṣ-Ṣiḥḥa into Latin are preserved in many manuscripts from the early modern period, and are thought to illustrate the relationship between medieval Europe and the Arab world in the field of medicine. Despite increased European contact with Egypt and Syria through the Crusades and trade into the 16th century, there are no Latin translations of Arabic medical texts after Ibn Buṭlān's era.
