The estates of the realm, or three estates, were the broad orders of social hierarchy used in Christendom from the Middle Ages to early modern Europe. Different systems for dividing society members into estates developed and evolved over time.The best known system is the French Ancien Régime, a three-estate system which was made up of clergy, nobles, peasants and bourgeoisie. In some regions, notably Sweden and Russia, burghers and rural commoners were split into separate estates, creating a four-estate system with rural commoners ranking the lowest as the Fourth Estate. In Norway, the taxpaying classes were considered as one, and with a very small aristocracy; this class/estate was as powerful as the monarchy itself. In Denmark, however, only owners of large tracts of land had any influence. Furthermore, the non-landowning poor could be left outside the estates, leaving them without political rights. In England, a two-estate system evolved that combined nobility and clergy into one lordly estate with "commons" as the second estate. This system produced the two houses of parliament, the House of Commons and the House of Lords. In southern Germany, a three-estate system of nobility, knights, and burghers was used. In Scotland, the Three Estates were the Clergy, Nobility, and Shire Commissioners, or "burghers", representing the bourgeois, middle class, and lower class. The Estates made up a Scottish Parliament.

The term Fourth Estate or fourth power refers to the press and news media both in explicit capacity of advocacy and implicit ability to frame political issues. The derivation of the term arises from the traditional European concept of the three estates of the realm: the clergy, the nobility, and the commoners. The equivalent term "fourth power" is somewhat uncommon in English, but it is used in many European languages, including German, Italian, Spanish, French, Swedish, Polish, and Russian to refer to a government's separation of powers into legislative, executive, and judicial branches.