The system of the three classes was a Voting system adopted in 1849 by the king Frederic-Guillaume IV of Prussia for the election of the House of Commons of Prussia. The poll was unequal, public and indirect. It was used in the Royaume of Saxony until 1909 and in the Royaume of Prussia, the duchy of Brunswick and the Principauté of Waldeck until 1918, before being replaced by an equal, secret and direct system. It was also used in certain part of Prussia for the local elections.

Within the framework of this system, the Electorate, which included/understood twenty-four years the major men, was divided into three classes so that each class had the same volume of direct imposition: the first class corresponded to the higher third of the scale of imposition, the second class with the intermediate third, and the third class with the lower third. Although the classes included/understood a very unequal number voters, each one elected the same number of Great Electors. Thus, in 1849, the first class included/understood 4,7% of the population, the second class, 12,7%, and the third class, 82,6%; the voters of the first class, who paid the most tax and were richest, were surreprésentés taking into consideration their number, in a proportion of 17,5 to 1 compared to the voters of the third class. Imbalance between classes many voters was sometimes particularly strong: at the time of the local elections with Essen, the industrialist Alfred Krupp was the only voter of the first class.

The poll being public, the voters expressed their vote orally. The Great Electors ( of Wahlmänner ) elected then the deputies within the framework of the districts.

In 1871, the male, equal and secret vote for all was adopted for the election of the Reichstag, but the system of the three classes was preserved in Länder where it was applied. The dominant position of the kingdom of Prussia, which covered more of two thirds of the territory of the German Reich, placed its electoral system in the middle of the claims of political reforms. The system was however maintained for all the imperial period, because it allowed the conservatives, constant by the easy and surreprésentées classes, to be maintained with the capacity. The social democrats had for example only one about fifteen seats with the House of Commons Prussia, while an identical electoral result in term of voice ensured to them a hundred deputies to the Reichstag.

In 1917, whereas the opposition to the continuation of the World war progressed and that the democratic camp gained in audience, the chancellor Bethmann-Hollweg prepared a reform project of the electoral system, that the emperor Guillaume announced on April 7th at the time of its message of Easter to the House of Commons of Prussia. However, the project, because of its moderation and of the absence of date of implementation, failed to calm the dissatisfaction of the public opinion. The following year, the Révolution of November reversed the imperial institutions and involved the end of the system of the three classes; article 17 of the Constitution of Weimar proclaimed the equality and the secrecy of the vote and granted the right to vote with all citizens of the two sexes and major twenty years.