Speaking of the last days, the Lord declared through the ancient Israelite prophet Malachi that Elijah would return "before the coming of the great and dreadful day of the Lord" (Mal. 4:5). And through the prophet Joel, the Lord foretold signs in the heavens "before the great and the terrible day of the Lord come" (Joel 2:31). Jesus' Second Coming is the "day of the Lord" referred to in these prophecies. Many Latter-day Saints interpret the phrase "the great and dreadful [or terrible] day of the Lord" to mean the Lord's Second Coming will be "great," or good and desirable, for the righteous, but "dreadful" for the wicked, who will be destroyed. However, this interpretation misrepresents the original meaning of the phrase. For one thing, the Hebrew language in which this expression was orignally written does not support this explanation. For another, the English word "great" was not used with the modern meaning "desirable" until long after the King James Version was translated. This study will elucidate the meaning of the expression "the great and dreadful/terrible day of the Lord" by (1) examining the Hebrew grammar and vocabulary behind the English translation of Joel 2:31 and Malachi 4:5; (2) considering the broader biblical context in which this expression occurs; (3) highlighting modern prophetic statements that pertain to the meaning of this expression; and (4) comparing this expression with other "great and ___" formulations in scripture.