Riksdag of the Estates (formally Swedish: Riksens ständer; informally Swedish: Ståndsriksdagen) was the name used for the Estates of Sweden when they were assembled. Until its dissolution in 1866, the institution was the highest authority in Sweden next to the King.It was a Diet made up of the Four Estates, which historically were the lines of division in Swedish society:

The roots of the modern Riksdag can be found in a 1435 meeting in the city of Arboga; however, only three of the estates were probably present: the nobility, the clergy and the burghers. This informal organization was modified in 1527 by the first modern Swedish king Gustav I Vasa to include representatives from all the four social estates: the nobility, the clergy, the burghers …