The Great Disappointment was an event in the early history of certain Christian denominations, when Jesus failed to re-appear on the appointed day of October 22, 1844 as some Christians expected.

Between 1831 and 1844, William Miller, a Baptist preacher, launched what he called the "great second advent awakening", also known as the Millerite Movement. Miller preached a set of fourteen rules for the interpretation of the Bible, which spread to followers throughout the world. Based on his study of the prophecy of Daniel 8:14, Miller calculated that Jesus would return to Earth sometime between 1843 and 1844. Others within the movement calculated a specific date of October 22, 1844.

When Jesus did not appear, Miller's followers experienced what came to be called "the Great Disappointment". Most of the thousands of followers left the movement. A few, however, went back to their Bibles to find why they had been disappointed. They concluded that the prophecy predicted not that Jesus would return to earth in 1844, but that a special ministry in heaven would be formed on that date. Miller rejected his own movement altogether.

Interestingly, members of the Bahá'í Faith believe that the Great Disappointment wasn't a disappointment at all, and was in fact referring to the advent of their twin prophets the Báb and Bahá'u'lláh.