An ideology is a collection of ideas. Typically, each ideology contains certain ideas on what it considers to be the best form of government (e.g. autocracy or democracy) and the best economic system (e.g. capitalism or socialism). The same word is sometimes used to identify both an ideology and one of its main ideas. For instance, socialism may refer to an economic system, or it may refer to an ideology that supports that economic system. The same term may also refer to multiple ideologies, which is why political scientists try to find consensus definitions for these terms. For example, while the terms have been conflated at times, communism has come in common parlance and in academics to refer to Soviet-type regimes and Marxist–Leninist ideologies, whereas socialism has come to refer to a wider range of differing ideologies which are most often distinct from Marxism–Leninism.
The following list is strictly alphabetical and attempts to divide the ideologies found in practical political life into several groups, with each group containing ideologies that are related to each other. The headers refer to the names of the best-known ideologies in each group. The names of the headers do not necessarily imply some hierarchical order or that one ideology evolved out of the other. Instead, they are merely noting that the ideologies in question are practically, historically, and ideologically related to each other. As such, one ideology can belong to several groups and there is sometimes considerable overlap between related ideologies. The meaning of a political label can also differ between countries and political parties often subscribe to a combination of ideologies.