The Great Disappointment of 1844 refers to the significant event in American religious history when a large group of Millerites, followers of William Miller, anticipated the Second Coming of Christ on October 22, 1844, but were left disillusioned when it did not occur. This event not only marked a pivotal moment in the development of new religious movements but also led to the establishment of various sects and interpretations that emerged in response to this unfulfilled prophecy.