Al-Bīrūnī (ca. 973-1050) was an innovative encyclopaedist thinker. He is particularly known to have investigated into India of his time. Yet, his life and the circumstances of his encounter with Indian languages, culture and sciences are still shrouded in mystery and legends. This research brings to light elements of his intellectual journey based on well-grounded analysis so as to contextualise al-Bīrūnī's work of transmission of Indian philosophies into Arabic. Thanks to a theoretical framework rooted in a multidisciplinary approach, including Translation Studies, it enables to comprehend the full scope of his work and to analyse deeply his motives and choices of interpretation.