The earliest Christian-Muslim dialogue offers a unique glimpse into how Christians viewed the religion of their neighbors. Much of contemporary American scholarship misplaces focus geographically and linguistically in the West, chronologically late, and theologically narrow. These biases neglect those who had the earliest interaction with Islam, allowing for misunderstanding of how Christians originally understood Islam. This study examines the apologetic arguments of representatives under Islamic rule, in the late 7th to early 9th centuries, and both inside and outside theological orthodoxy, to understand how they used Christology to distinguish Christianity from Islam, whether as a heretical group or a distinct religious system. Each Christological group interacted with other Christians in one manner and with Muslims in a different manner. They contextualized their Christology in an attempt to build bridges between Christians and Muslims, with syncretistic tendencies being generally avoided. Given the terminology and analogies used by each group, this study found that the earliest Christians to engage Islam argued it was a religious system that was distinct from Christianity rather than a Christian heresy.