Qusta ibn Luqa (820–912) (Costa ben Luca, Constabulus) was a Melkite physician, scientist and translator, of Byzantine Greek extraction. He was born in Baalbek. Travelling to parts of the Byzantine Empire, he brought back Greek texts and translated them into Arabic.
Qusta ibn Luqa al-Ba'albakki, i. e. from Baalbek or Heliopolis, Lebanon, a Melkite Christian of Greek origin, was born in 860 and flourished in Baghdad. He was a philosopher, physician, mathematician and astronomer. He died in Armenia in A.D. 912.
Translations of Diophantos, Theodosius of Bithynia's Sphaerica, Autolycus, Hypsicles, Aristarchus, Theophrastus’ Meteora, Galen’s catalogue of his books, Hero of Alexandria's (Heron's) Mechanics, and John Philoponus were made or revised by him, or made under his direction. He wrote commentaries on Euclid and a treatise on the Armillary sphere. He was a prominent figure in the Graeco-Arabic translation movement that reached its peak in the 9th century. At the request of wealthy and influential commissioners, Qusta translated Greek works on astronomy, mathematics, mechanics and natural science into Arabic. He also produced works of his own: more than sixty treatises are attributed to him. He wrote mainly on medical subjects, but also on mathematics and astronomy. Only a small part of his production has so far been edited. The extant editions of Qusta’s medical works show that he was thoroughly acquainted with Hippocratic-Galenic humoral medicine– the theoretical system that constituted the basis of formal medicine in Islam.
His original works, many listed in the Fihrist of Ibn al-Nadim, dealt with contemporary science, medicine, astronomy and philosophy. A Latin translation of his work ‘On the Difference between the Spirit and the Soul’ (De Differentia Spiritus et Animae) was one of the few works not attributed to Aristotle that was included in a list of ‘books to be 'read,' or lectured on, by the Masters of the Faculty of Arts, at Paris in 1254, as part of their study of Natural Philosophy. This translation was made by Joannes Hispalensis, (John of Seville, fl. 1140). He wrote a treatise on Nabidh. His Medical Regime for the Pilgrims to Mecca: The Risālā Fī Tadbīr Safar Al-ḥa is available in translation.
Of him Ibn al-Nadim says: "He is an excellent translator; he knew well Greek, Syriac, and Arabic; he translated texts and corrected many translations. Many are his medical writings."  Qusta was with Hunayn Ibn Ishaq the author who best served Greek culture in the Arab civilization.
Involvement with peers
He was also involved, with his fellow-Christian Hunayn ibn Ishaq, in an epistolary exchange with the Muslim astronomer, Abu Isa Yahya ibn al-Munajjim, who had invited them to embrace Islam. Both refused, and provided their reasons for rejecting al-Munajjim's Islamic faith. 
- Risalah fī Auja Al Niqris by Qusta Ibn Luqa. Edited with translation and commentary by Hakim Syed Zillur Rahman, Ibn Sina Academy of Medieval Medicine and Sciences, Aligarh, 2007 (ISBN 978-81-901362-8-0).
- Rislah fī al Nabidh (Arabic translation of Qusta ibn Luqa by Rufus. Edited with translation and commentary by Hakim Syed Zillur Rahman, Ibn Sina Academy of Medieval Medicine and Sciences, Aligarh, 2007 (ISBN 978-81-901362-7-3).
- Rîsâlah-i Nabîdh of Qustâ bin Lûqâ by Hakim Syed Zillur Rahman, Supplement to 'Studies in the History of Medicine and Science' (SHMS), Jamia Hamdard, Vol. IX(1985), pp. 185–201.
- Kitāb fī al‐ʿamal bi‐ʾl–kura al‐nujūmiyya (On the use of the celestial globe; with some variations as to title), which contains 65 chapters and was widely disseminated through at least two Arabic recensions as well as Latin, Hebrew, Spanish, and Italian translations
- the extant astronomical work, Hayʾat al‐aflāk (On the configuration of celestial bodies; Bodleian Library MS Arabic 879, Uri, p. 190), which is one of the earliest compositions in theoretical (hayʾa) astronomy
- Kitāb al‐Madkhal ilā ʿilm al‐nujūm (Introduction to the science of astronomy – astrology)
- Kitāb al‐Madkhal ilā al‐hayʾa wa‐ḥarakāt al‐aflāk wa‐ʾl‐kawākib (Introduction to the configuration and movements of celestial bodies and stars)
- Kitāb fī al‐ʿamal bi‐ʾl‐asṭurlāb al‐kurī (On the use of the spherical astrolabe; Leiden University Library MS Or. 51.2: Handlist, p. 12)
- Kitāb fī al‐ʿamal bi‐ʾl‐kura dhāt al‐kursī (On the use of the mounted celestial sphere).
- Nancy G. Siraisi, Medicine and the Italian Universities, 1250-1600 (Brill Academic Publishers, 2001), p 134.
- J. A Burns, article on ‘The Faculty of Arts’ in The Catholic Encyclopedia, Vol. 1, [NY: Robert Appleton, 1907], 758.
- Lūqā, Qusṭā ibn; Bos, Gerrit (1992). Qusṭā Ibn Lūqā's Medical Regime for the Pilgrims to Mecca: The Risālā Fī Tadbīr Safar Al-ḥajj. BRILL.
- see Ibn al-Nadim, Fihrist, ed. Fugel, p. 234.
- Sydney H. Griffith, The Church in the Shadow of the Mosque: Christians and Muslims in the World of Islam, Jews, Christians, and Muslims from the Ancient to the Modern World (Princeton University Press, 2008), p. 86; Samir Khalil Samir and Paul Nwyia, Une correspondance islamo-chrétienne entre ibn al-Munaggim, Hunaym ibn Ishaq et Qusta ibn Luqa, Patrologia Orientalis, 40:4, no. 185 (Turnhout: Brepols, 1981).
- Kheirandish, Elaheh (2007). "Qusṭā ibn Lūqā al‐Baʿlabakkī". In Thomas Hockey et al. The Biographical Encyclopedia of Astronomers. New York: Springer. pp. 948–9. (PDF version)
- Les Arabes et les Arméniens à l'époque médiévale
- Harvey, L. Ruth (2008) [1970-80]. "Qusṭā Ibn Lūqā Al-BaʿLabakkī".