Midsummer, also referred to as Litha by some Wiccans and other Neopagans, refers to the period of time centered upon the summer solstice and the religious celebrations that accompany it. Also called "Midsommar" in Swedish, Midsummer-related holidays, traditions and celebrations, many of which are non-Christian in origin (apart from the designation "St John's Day"), are particularly important in Finland and Sweden, but found also in other parts of Northern Europe, Britain and elsewhere.

The name Litha comes from Bede's De Tempore Rationum in which he gave the Anglo-Saxon names for the months roughly corresponding to June and July as "se Ærra Liþa" and "se Æfterra Liþa" (the early Litha month and the later Litha month) with an intercalendary month of "Liþa" appearing after se Æfterra Liþa on leap years.

The term Litha probably came into modern Neopagan use in three ways, the degree of influence of one upon the other being hard to tell:

1. The writings and ritual calendar used by Aidan Kelly.
2. Attempts to reconstruct and reintroduce the Anglo-Saxon calendar.
3. The fictional calendar used in the works of Tolkien (this was probably not a direct influence, but rather influenced the popularity of the name).

Solstitial celebrations still centre upon 24th June, which is no longer the longest day of the year. The difference between the Julian calendar year (365.2500 days) and the tropical year (365.2422 days) moved the day associated with the actual astronomical solstice forward approximately three days every four centuries until Pope Gregory XIII changed the calendar bringing the solstice to around 21st June. In the Gregorian calendar, the solstice moves around a bit but in the long term it moves only about one day in 3000 years.