Ja'far ibn Yahya Barmaki, Jafar al-Barmaki (Persian: ? ? , Arabic: ? ?, ja`far bin ya?y?) (767-803) was a Persian vizier of the Arab Abbasid caliph Harun al-Rashid, succeeding his father (Yahya ibn Khalid) in that position. He was a member of the influential Barmakid family, formerly Buddhist leaders of the Nava Vihara monastery. Along with the rest of the Barmakids, he was executed in 803 at the orders of Harun al-Rashid. It is said that his execution was for allegedly having had an affair with Harun's sister Abbasa, although historical sources remain unclear.
He had a reputation as a patron of the sciences, and did much to introduce Indian science into Baghdad. He was credited with convincing the caliph to open a paper mill in Baghdad, the secret of papermaking having been obtained from Tang Chinese prisoners at the Battle of Talas (in present-day Kyrgyzstan) in 751.
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Ja'far also appears (under the name of Giafar in most translations) along with Harun al-Rashid in several Arabian Nights tales, often acting as a protagonist. In "The Three Apples" for example, Ja'far is like a detective who must solve a murder mystery and find the culprit behind the murder, whereas in "The Tale of Attaf", Ja'far is more of an adventurer. In Glenn Pierce's novel The Tyrant of Bagdad, Ja'far's story is told through a fictional account of Charlemagne's ambassador's travel to meet with Harun al-Rashid.
However, more recent media inspired by the Arabian Nights has portrayed Ja'far as both a villain and a sorcerer: