Maulana Abdul Haq Vidyarthi (1888–1977), a scholar of world religions & languages, joined the Ahmadiyya Movement in 1907, drawn by its universal respect for all revealed faiths. He earned the title Vidyarthi for his deep knowledge of the Hindu Vedas. In 1914, he joined the Lahore-based Ahmadiyya Anjuman Isha‘at Islam, where he worked lifelong as a missionary, writer, & debater. He mastered Sanskrit, Hebrew, & ancient religious texts to (1) defend Islam from Arya Samaj & Christian critiques, & (2) trace prophecies about Prophet Muhammad in earlier scriptures. Between 1918 and the 1940s, he represented Islam in many public debates across India, achieving legendary success. His Urdu responses to objections became widely read. He also translated parts of the Yajur Veda. After Partition, he toured Trinidad, Guyana, Suriname, and Fiji in the 1950s, earning great acclaim. From 1959–1962, he researched in the U.S. for the expanded English edition of Muhammad in World Scriptures, originally Mithaq-un-nabiyyin (1936). Its 3-volume second edition appeared between 1966 & 1975. Revered for both scholarship & saintliness, he was humble, humorous, & devoted. His sixty years of service to Islam by pen, debate, and piety remain unmatched and unforgettable in religious history.