John Cook Bennett (August 3, 1804 – August 5, 1867) was an American physician and briefly a ranking and influential leader of the Latter Day Saint movement, who acted as mayor of Nauvoo, Illinois, and Major-General of the Nauvoo Legion in the early 1840s.

Bennett's involvement in the Latter Day Saint movement came after several encounters with the community that had left him impressed. He therefore wrote several letters to Joseph Smith in Nauvoo, Illinois, in which he declared his desire to join the Church of Jesus Christ of Latter Day Saints. Bennett was essential to the passing of the Nauvoo city charter in the Illinois Legislature, the provisions of which he had helped craft. He even garnered praise for his lobbying efforts on behalf of the Mormons from the young Abraham Lincoln.

His efforts on behalf of the Mormons and the long time he spent living in the Mansion House in Nauvoo secured for Bennett the confidence of Smith. Smith was instrumental in promoting Bennett to ever greater civic and ecclesiastical responsibilities in Nauvoo. Bennett became a Counselor in the First Presidency, the mayor of Nauvoo, General of the Nauvoo Legion, and the chancellor of Nauvoo University.