Baha'uddin 'Ali ibn Ahmad ibn ad-Dayf, also known as Al-Muqtana Baha'uddin, Baha'uddin al-Muqtana, Bahā'a ad-Dīn, Bahā'a ad-Dīn, Ali ibn Ahmad, Baha' al-Din, Ali ibn ad-Dayf, Ali b ad-Tai or Baha'u d-Din as-Samuqi (born 979 – died 1043 CE) was an 11th-century Ismaili, and founding leader of the Druze. He was born in a small village called Sammuqa near Aleppo in Syria and belonged to the Arab tribe of Tayy.
Al-Muqtana was appointed as a governor of Apamea, Syria, by Al-Hakim bi-Amr Allah, for whom he captured Aleppo from the Hamdanid dynasty in 1016. In 1017 he took the captive Abdurrahim ibn Ilyas from Damascus to Cairo after the latter' deposition by Al-Hakim. Along with Hamza ibn-'Ali ibn-Ahmad, he was one of seven believers who had defended the Raydan Mosque (near the Al-Hakim Mosque) successfully against twenty thousand attackers. Al-Muqtana was second in rank only to Hamza in the Druze movement and became known as the "left wing" to Hamza's "right wing". He was a prominent leading figure, especially after the disappearance of Al-Hakim, and became the leader of the Druze in 1021, after the onset of persecutions by Al-Hakim's successor Ali az-Zahir, while Hamza went into hiding. Al-Muqtana resumed activities and coordinated the Divine call from 1027 onwards until he went into hiding as well in 1037. He continued writing until 1043, when the first Divine call ended and new conversions to become Druze were prohibited.
Around 1035, a rebellion within the Druze movement was led by a Syrian apostate, Sukayn. After a male messenger was murdered in the Wadi al-Taym, Lebanon, Al-Muqtana dispatched a delegation under a female Druze called Sarah, who may have been his niece. Sarah was renowned for her mission's success and demonstrating her sincerity of faith and knowledge. Her story is thought to have exemplified the gender equality of the new faith.
Al-Muqtana wrote on a variety of subjects, ranging from universal intelligence to metempsychosis, and taught that "only the believer who applies himself to acquiring the sciences and truths leading to tawhid is exempt from the performance of ritual obligations."
A shrine dedicated to Baha' ad-Din, probably identical with Al-Muqtana, is located at the Druze village of Beit Jann in Upper Galilee, Israel.