John C. Hamer is an American-Canadian historian and mapmaker. His research has focused primarily on the history of the Latter Day Saint movement, authoring several books on the topic. Hamer is a leading expert on various schisms within especially non-far-Western (U.S.) portions of the Latter Day Saint "Restoration" movement. Raised in the Church of Jesus Christ of Latter-day Saints (LDS Church), Hamer left the religion before joining Community of Christ in 2010 and now serves as Pastor of its Toronto Congregation. Hamer was a contributor to By Common Consent, the Restoration Studies Coordinator at Sunstone Education Foundation, and the Executive Director of the John Whitmer Historical Association.