Midsummer is a celebration of the season of summer occurring near the date of the summer solstice which is known in solar reckoning as the mid-point of the season. As the precise date of the summer solstice can vary from year to year, different traditions may celebrate or fix Midsummer at different dates or under different names occurring on or around the actual solstice. A variety of traditions have developed often rooted in regional, spiritual, or religious practices. Traditionally, Midsummer is on the first Saturday after June 20th, though it is often celebrated on Midsummer's Eve, on the day before.

Summer is the hottest and brightest of the four temperate seasons, occurring after spring and before autumn. At or centred on the summer solstice, daylight hours are the longest and darkness hours are the shortest, with day length decreasing as the season progresses after the solstice. The earliest sunrises and latest sunsets also occur near the date of the solstice. The date of the beginning of summer varies according to climate, tradition, and culture. When it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere, and vice versa.