Centrism is the range of political ideologies that exist between left-wing politics and right-wing politics on the left–right political spectrum. It is associated with moderate politics, including people who strongly support moderate policies and people who are not strongly aligned with left-wing or right-wing policies. Centrism is commonly associated with liberalism, radical centrism, and agrarianism. Those who identify as centrist support gradual political change, often through a welfare state with moderate redistributive policies. Though its placement is widely accepted in political science, radical groups that oppose centrist ideologies may sometimes describe them as leftist or rightist.

Centrist parties typically hold the middle position between major left-wing and right-wing parties, though in some cases they will hold the left-leaning or right-leaning vote if there are no viable parties in the given direction. Centrist parties in multi-party systems hold a strong position in forming coalition governments as they can accommodate both left-wing and right-wing parties, but they are often junior partners in these coalitions and are unable to enact their own policies. These parties are weaker in first-past-the-post voting than proportional representation systems. Parties and politicians have various incentives to move toward or away from the centre, depending on how they seek votes. Some populist parties take centrist positions, basing their political position on opposition to the government as opposed to left-wing or right-wing populism.

Centrism developed with the left–right political spectrum during the French Revolution, when assemblymen associated with neither the radicals nor the reactionaries sat between the two groups. Liberalism became the dominant centrist ideology in the 18th century with its support for anti-clericalism and individual rights, challenging both conservatism and socialism. Agrarianism briefly existed as a major European centrist movement in the late-19th and early-20th centuries. The eugenics associated with the Holocaust caused centrists to abandon scientific racism in favour of anti-racism. Centrism became more influential after the dissolution of the Soviet Union as it spread through Europe and the Americas, but it declined in favour of populism after the 2008 financial crisis.

As with all ideological groups, the exact boundaries of what constitutes centrism are not perfectly defined; however, its specific placement on the left–right political spectrum makes its position clearer relative to other ideologies. Centrism most commonly refers to a set of moderate political beliefs between left-wing politics and right-wing politics. Individuals who describe themselves as centrist may hold strong beliefs that align with moderate politics, or they may identify as centrist because they do not hold particularly strong left-wing or right-wing beliefs. In some cases, individuals who simultaneously hold strong left-wing beliefs and strong right-wing beliefs may also describe themselves as centrist. Although the left-centre-right trichotomy is well established in political science, individuals far from the political centre may occasionally reframe it, with the far-right alleging that the centre is leftist and the far-left alleging that the centre is rightist. Likewise, they may allege that their more moderate counterparts, the centre-left and the centre-right, are actually centrists because they are insufficiently radical.

Liberalism is commonly associated with the political centre. Both left-leaning and right-leaning variants of liberalism may be grouped within a broader understanding of centrism. In Europe, left-leaning liberalism emphasises social liberalism and is more common in nations with strong conservative movements, while right-leaning liberalism emphasises economic liberalism and is more common in nations with strong Christian democratic movements. Social liberalism combines centrist economic positions with progressive stances on social and cultural issues. Left-leaning liberalism generally sits closer to the centre than right-leaning liberalism.

Parties associated with social democracy and green politics commonly adopt the liberal position on social issues. Green parties, usually associated with left-wing politics, have a history of centrist economic policies in Central and Eastern Europe. Christian democracy, often considered a centre-right ideology, is sometimes grouped with the centre. Agrarianism may also be grouped with the centre. Agrarian parties are associated with the interests of farmers and other people associated with agriculture. Decentralization and environmental protection are also major agrarian ideals. These parties often developed in European countries where there was not a strong liberal movement, and vice versa, but they became less relevant by the mid-20th century.

Radical centrism is a form of centrism defined by its rejection of the left–right dichotomy or of ideology in general. Liberal scepticism and neo-republicanism can both be elements of radical centrism. Third Way politics is a radical centrist approach taken by centre-left parties to find a middle ground between capitalism and socialism. Though populism is commonly associated with strong left-wing or right-wing beliefs, centrist populism is critical of the political system independently of social, economic, and cultural issues. Centrist populist parties often do not have a strong ideological component, instead making anti-establishment politics the core of their message to capitalise on voter dissatisfaction and receive protest votes. These parties are most common in Central and Eastern Europe.

Centrism advocates gradual change within a political system, opposing the right's adherence to the status quo and the left's support for radical change. Support for a middle class is a defining trait of centrism, holding that it is preferable to reactionary or revolutionary politics. In contemporary politics, centrists generally support a liberal welfare state. Centrist coalitions are associated with larger welfare programs, but they are generally less inclusive than those organised under social democratic governments. Centrists may support some redistributive policies, but they oppose the total abolition of the upper class. Centrist liberalism seeks institutional reform, but it prioritises prudence when enacting change. European centrist parties are typically in favour of European integration and were the primary movers in the development of the European Union. Whether political positions are considered centrist can change over time; when radical positions become more widely accepted in society, they can become centrist positions.