Philip Jenkins (The Lost History of Christianity) says that Christianity is so similar to Islam that earlier in the eighth century, Saint John Damascene saw Islam not as a new religion but as a Christian heresy, the sect of the Ishmaelites or Hagatenes. Damascene wrote, "From that time to the present, a false prophet named Mohammed has appeated in their midst. This man, after having chanced upon the Old and New Testaments and likewise, it seems, having conversed with an Arian monk, devised his own heresy." Even through the Middle Ages, Christians saw Muhammad as a schismatic rather than the leader of an new and alien faith.
Jenkins says that the connection between Islam and older Eastern forms of Christianity is so intimate as to raise unsettling questions for modern-day members of both faiths. Apart from worshipping the same God and recognising the same prophets, Islam especially in its early days was almost indistinguishable from Eastern versions of Christianity. The Christian impact on Islam was profound, and can be traced at the deepest roots of that faith.
While many Muslim beliefs and practices now seem strange and different to Christians, this is because Islam's similarities are to Nestorian Christianity, which is now almost vanished, and to Gnostic Christianity. Most of the Quranic stories about Mary and Jesus find their parallels not in the four biblical gospels but in apocryphal texts that circulated widely in the East, such as the Protevangelium of James and the Arabic Infancy Gospel. The Quran also presents the death of Jesus in exactly the language of Eastern Christians known as the Docetists, who saw the event as an illusion rather than a coricrete reality: "They did not kill him and they did not crucify him, but it was made to seem so to them."
So strong are these connections that over the past half century scholars have questioned whether the Quran could even have originated in Arabia, or whether it was collected or constructed somewhere else with a prominent Christian and Jewish population, perhaps in Syria or Mesopotamia.
Another answer from our community:
They believe in somethings that's not real or not going to happen.
They are Monotheistic ( believe in one god)
They're similar in the fact that they have one god (Allah in Islam, Yahweh in Christianity.)
Christianity, Islam, Judaism & even Baha'i all have a mutual ancestor: Abraham.
Christianity, Judeaism, and Islam are similar. they believe in the same God and have a shared History. the Story splits with Abraham.
Christianity and Islam have similar religious roots in the Middle East although what was believed about individual characters represented may diverge very greatly. For example, in Christianity Jesus is the savior, but in Islam he is a prophet.
Judaism Christianity and Islam all are...Monotheistic Religions.
Judaism, Christianity, Sikhism, Zoroastrianism, & Baha'i.
Islam, Judaism and Christianity.
Islam, Christianity
Christianity, Islam
Heaven, hell, and a final judgement
The Bible is to Christianity as the Qur'an (Koran) is to Islam.
Judaism, Christianity, and Islam have all claimed the Holy Land for themselves.