In politics, coalition is commonly used to describe the coming together of a number of individuals or groups to pursue a certain end. They are alliances of "parties, persons or states without permanent incorporation into one body." (OED).

Coalition is considered the most peaceful of outcomes in the struggle for power, but how peaceful depends upon the institutional context and the decision rules for resolving the conflicts among individuals and their coalitions, in the form of informal agreements, arbitration, or constitutional procedures. This becomes clear by distinguishing among coalitions formed within civil society or the legislature, by groups or political parties.

Coalition became one of the central concerns of 20th century political science (as well as for practical politics) because "the interest" (not the individual) was adopted as the atomic unit of political analysis. Although individuals are the bearers of interests, it is the interest that is played out through conflict and accommodation in the political process (LLQ). This is the basis of electoral coalitions, referring to the efforts by political parties to conduct campaign appeals in such a manner as to attract voters from various communities or class surroundings to provide a base for representation (LRQ). With respect to parliamentary coalitions, emphasis in the US has been on coalitions of groups formed to pressure (or lobby) governments toward preferred policies (ULQ). By contrast, the focus in European settings is more toward coalitions of political parties to form a governmental majority (URQ).