Marcionism was a competing interpretation of Christian doctrine during the first phase of Christianity. Marcion of Sinope's writings were well known in the second century but there are no surviving transcriptions. What is known of the belief system comes from writings originating in what became the Catholic Church that condemned his views.
Marcion accepted the Christian belief in Jesus Christ as humanity's saviors sent by God, and he accepted the letters from Apostle Paul and a selection from the Gospel of Luke. The rest of the books that became the New Testament he rejected along with the Hebrew Bible, which became the Old Testament. In some respects Marcion's beliefs were similar to Christian Gnosticism. He took the cruel deity of the Old Testament as non-identical with the supremely good God revealed in the teachings of Jesus, though the system as reconstructed through surviving criticisms differs enough from the Gnostics in other respects that it is usually classified separately.
The doctrine advocated by Marcion survived significantly longer than did the Gnostic school, and even as an active religious group and practice Marcionism continued for several centuries. This can in part be attributed to Marcion's wealth and social position. Though he was excommunicated from the Catholic Church, his father was a bishop and he was a wealthy merchant himself. He put his considerable wealth toward organizing and promoting his own sect, a financial advantage most of the other sects competing with the established Church did not enjoy. Despite the relative success of those early years, eventually Marcion's writings were lost and Marcionism died out.