Izhar ul-Haqq (The Demonstration of Truth) is a monumental polemical work by the 19th-century Indian Islamic scholar Rahmatullah bin Khalilur Rahman al-Hindi. This influential book systematically refutes Christian theological doctrines, including the Trinity, the divinity of Jesus, and the crucifixion. It meticulously scrutinizes the textual integrity and historical authenticity of the Bible, highlighting perceived contradictions and alterations. Written in response to the famous Agra Debate with Christian missionaries, the book served as a powerful defense of Islamic beliefs and a critique of Christian polemics, becoming a foundational text for Islamic apologetics worldwide.