Gustav Adolfsdagen (Swedish for Gustavus Adolphus Day) is a general flag day, celebrated in Sweden on November 6 in memory of king Gustavus Adolphus of Sweden (Swedish: Gustav II Adolf), who was killed on this day in 1632 at the Battle of Lützen. Gustav Adolfsdagen coincides with the Finnish Swedish Heritage Day.
The date has been celebrated since the early 19th century. It is especially popular in Gothenburg, which was founded by Gustavus Adolphus, and in Uppsala, where the king donated a lot of money to the university.