A blue supermoon is a rare astronomical event that occurs when a full moon coincides with two other lunar phenomena: a supermoon and a blue moon. A supermoon is a full moon that occurs when the moon is at its closest point to Earth in its orbit, making it appear larger and brighter than usual. A blue moon is the second full moon in a calendar month, which happens about once every two to three years. When all three of these events occur simultaneously, it is called a blue supermoon.

Despite its name, a blue supermoon does not actually appear blue in color. The term "blue" refers to the rarity of the event, rather than the color of the moon itself. The last blue supermoon occurred on August 31, 2023. The next one is expected to occur in 2037.