A multi-party system is a system in which multiple political parties have the capacity to gain control of government separately or in coalition, e.g. The Christian-Democratic Union of Germany and Christian Social Union in Bavaria (CDU/CSU) in a Coalition with the Free Democratic Party (FDP) set up after the 2009 Federal elections. The effective number of parties in a multi-party system is normally larger than two but lower than ten. It is a system where there are large amounts of major and minor political parties that all hold a serious chance of receiving office, and because they all compete, a majority may not come to be, forcing the creation of a coalition.

A party system is a concept in comparative political science concerning the system of government by political parties in a democratic country. The idea is that political parties have basic similarities: they control the government, have a stable base of mass popular support, and create internal mechanisms for controlling funding, information and nominations.

The concept was originated by European scholars studying the United States, especially James Bryce and Moisey Ostrogorsky, and has been expanded to cover other democracies.Giovanni Sartori devised the most widely used classification method for party systems. He suggested that party systems should be classified by the number of relevant parties and the degree of fragmentation. Party systems can be distinguished by the effective number of parties.

Two structures of party system have been identified in the European Parliament since its first universal direct election in 1979, albeit the main EU party groups remained the same:

Italian party systems are usually considered only since the foundation of the Italian Republic (1946) as pre-fascist parties lacked a wide popular base.