This SpringerBrief is comprehensive account of the functions and effects of the Epstein-Barr virus (EBV) EBNA1 protein that relate to EBV-associated cancers and evidence for EBNA1 contributions to these cancers. EBNA1 was the first EBV protein detected and the most critical for EBV latent infection. EBNA1 fulfills multiple functions at EBV genomes which have been described in many (sometimes confusing) reports over the last 28 years. While these were initially thought to be the only roles of EBNA1, many reports in recent years have shown that EBNA1 also directly affects cellular processes in...