Christianity and Islam are two of the world's largest monotheistic religions, and both trace their spiritual heritage to the Abrahamic tradition. They affirm the existence of one supreme God who is the creator, sustainer, and judge of the universe. Both religions believe that God is eternal, omnipotent, omniscient, merciful, just, and worthy of worship alone. They also accept divine revelation, moral accountability, the existence of prophets, and the reality of life after death. Despite these common foundations, Christianity and Islam differ significantly in their understanding of God's nature, relationship with humanity, revelation, and salvation. These differences have shaped the theological and philosophical outlooks of both traditions. Christianity teaches that there is one God who exists eternally in three distinct persons: the Father, the Son, and the Holy Spirit. This doctrine, known as the Trinity, is central to Christian theology. Christians do not believe in three gods but affirm that the three persons share one divine essence. Each person is fully God, equal in power, glory, and eternity, while remaining distinct in personal identity. The doctrine of the Trinity was formulated through the teachings of the New Testament and clarified by early Church councils such as the Council of Nicaea in 325 CE and the Council of Constantinople in 381 CE. Islam, in contrast, emphasizes the absolute unity and uniqueness of God through the doctrine of Tawhid. Allah is one, indivisible, and without partners, equals, or offspring. The Qur'an repeatedly stresses that associating anything with God, known as shirk, is the gravest sin. Surah Al-Ikhlas summarizes this belief by declaring that Allah is One, eternal, neither begets nor is begotten, and none is comparable to Him. Therefore, Islam rejects the Trinity as inconsistent with pure monotheism and considers it a misunderstanding of God's absolute unity. Another major theological difference concerns the identity of Jesus Christ. Christianity teaches that Jesus is the Son of God, the second person of the Trinity, who became incarnate in human form for the salvation of humanity. Christians believe that Jesus is fully divine and fully human. His incarnation demonstrates God's love and willingness to enter human history. His crucifixion and resurrection are considered the central events through which sin is defeated and eternal life is made available to believers. Islam reveres Jesus, known as Isa, as one of the greatest prophets but firmly denies his divinity. According to Islamic belief, Jesus was born miraculously to the Virgin Mary through God's command, but he remained a human messenger. The Qur'an rejects the claim that Jesus is the Son of God and denies that he was crucified in the manner described in Christian theology. Muslims believe that God raised Jesus to heaven and that he will return before the Day of Judgment. Thus, while Jesus occupies an honored place in Islam, he is never regarded as divine or worthy of worship. The concept of divine revelation also differs between the two traditions. Christianity teaches that God revealed Himself progressively through the Hebrew Scriptures, the prophets, and ultimately through Jesus Christ, who is regarded as the Word of God made flesh. The Bible, consisting of the Old and New Testaments, records this revelation and serves as the authoritative scripture for Christians. Many Christian denominations also recognize the role of Church tradition and theological interpretation in understanding divine revelation. Islam teaches that God's final and complete revelation was given to Prophet Muhammad through