A coalition government, or coalition cabinet, is a cabinet of a parliamentary government in which several parties cooperate. The usual reason given for this arrangement is that no party on its own can achieve a majority in the parliament. A coalition government might also be created in a time of national difficulty or crisis, for example during wartime, to give a government the high degree of perceived political legitimacy it desires whilst also playing a role in diminishing internal political strife. In such times, parties have formed all-party coalitions (national unity governments, grand coalitions). If a coalition collapses a confidence vote is held or a motion of no confidence is taken.
Coalition cabinets are common in countries in which a parliament is proportionally representative, with several organized political parties represented. It does not appear in countries in which the cabinet is chosen by the executive rather than by a lower house (such as in the United States). In semi-presidential systems such as France, where the president formally appoints a prime minister but the government itself must still maintain the confidence of parliament, coalition governments occur quite regularly.
A similar situation exists in Israel with its dozens of different parties (only once in its electoral history has one party managed to gain a majority of seats in the Knesset). The centre-right, Likud, thus forms coalitions with far-right and orthodox groups, while the Israeli Labor Party allies itself with the more leftist and pacifist parties, while various centrist parties can and do join either party.
In both countries, grand coalitions of the two large parties also occur, but these are relatively rare and large parties usually prefer to associate with small ones (though ironically, currently both Israel's and Germany's governments include the two largest parties). However, if none of the larger parties can receive enough votes to form their preferred coalition, a grand coalition might be their only choice for forming a government. This is the current situation in Germany: in early elections, the CDU/CSU did not garner enough votes to form a majority coalition with the FDP; similarly the SPD and Greens did not have enough votes to continue on with their formerly ruling coalition. A grand coalition government was subsequently forged between the CDU/CSU and the SPD. Partnerships like these typically involve carefully structured cabinets. The CDU/CSU ended up holding the Chancellory while, the SPD took the majority of cabinet posts.
In Ireland, coalition governments are quite common with a single party not having ruled since 1989. Coalitions are typically formed of two or more parties always consisting of one of the two biggest parties, Fianna Fail and Fine Gael and one or more smaller parties or independent members of parliament. The current government consists of Fianna Fail, the Green Party, the Progressive Democrats and supported by independents.
India's present governing coalition, the United Progressive Alliance, consists of 13 separate parties. In Finland, no party has had an absolute majority in the parliament since independence, and multi-party coalitions have been the norm. Finland experienced its most stable government (Lipponen I and II) since independence with a five-party governing coalition, so called "rainbow government". The Lipponen cabinets set the stability record, and were unusual in the respect that both moderate (SDP) and extreme left wing (Left Alliance) sat in the government with the major right-wing party (National Coalition). The current government (Vanhanen II) is a four-party coalition. Japan is experiencing coalition governments since 1990s, which came into existence in 1993 after the defeat of Liberal Democratic Party, and it is present till today. Israel's governing coalitions meanwhile can include up to nine parties and are notoriously unstable as a result.
In Australia, the conservative Liberal and National parties are united in an effectively permanent coalition. This coalition has become so stable, at least at the federal level, that Australia, in effect, has become a two-party system.
In the United Kingdom, coalition governments (sometimes known as National Governments) have only been appointed in times of national crisis. The most prominent was the National Government of 1931-1940. There were multi-party coalitions during both World Wars. Apart from this, when no party has had a majority, minority governments have been formed with one or more opposition parties agreeing to vote for the legislation governments need to function.
Those who disapprove of coalition governments believe that such governments have a tendency to be fractious and prone to disharmony. This is because coalitions would necessarily include different parties with differing beliefs and who, therefore, may not always agree on the correct path for governmental policy. Sometimes the results of an election are such that the coalitions which are mathematically most probable are ideologically infeasible, such as in Flanders or Northern Ireland. A second difficulty might be the ability of minor parties to play "kingmaker" and, particularly in close elections, gain far more for their support than their vote would otherwise indicate.
Coalition governments have also been criticized of sustaining a consensus on issues when disagreement and the consequent discussion would be more fruitful. To forge a consensus, the leaders of ruling coalition parties can agree to silence their disagreements on an issue to unify the coalition against the opposition. The coalition partners, if they control the parliamentary majority, can collude to make the parliamentary discussion on the issue irrelevant by consistently disregarding the arguments of the opposition and voting against the opposition's proposals — even if there is disagreement within the ruling parties about the issue.
Powerful parties can also act in an oligocratic way to form an unholy alliance to stifle the growth of emerging parties. Of course, such an event is rare in coalition governments when compared to two-party systems, which typically exists because of stifling the growth of emerging parties, often through discriminatory ballot access regulations and plurality voting systems, etc.
A single, more powerful party can shape the policies of the coalition disproportionately. Smaller or less powerful parties can be intimidated to not openly disagree. In order to maintain the coalition, they will have to vote against the party's platform in the parliament. If they do not, the party has to leave the government and loses executive power.