This is a list of political parties in the United Kingdom.

The most significant political parties in England:

• Conservative Party - A centre-right to right-wing party which promotes British conservatism.
• Labour Party - A centre-left party which promotes social democracy.
• Liberal Democrats - A centrist party which promotes liberalism and federalism.
• Green Party of England and Wales - A left-wing party which promotes green politics, eco-socialism and republicanism.
• Reform UK - A right-wing, Eurosceptic and right-wing populist party that was originally founded as the Brexit Party in November 2018, before being re-named to Reform UK in January 2021.

Parties represented in the Scottish Parliament and/or in the House of Commons of the United Kingdom are:

• Scottish National Party (SNP) - A party mainly focused on achieving Scottish independence from the United Kingdom. It is a centre-left party which promotes social democracy.
• Scottish Greens - A centre-left to left-wing party which promotes green politics, Scottish independence and Scottish republicanism.
• Alba Party - A pro-independence and socially conservative party that runs candidates on the list only, to make an independence “supermajority”.

• Scottish Labour Party - A centre-left party which promotes social democracy.
• Scottish Conservative Party - A centre-right party which promotes conservatism and strong unionism.
• Scottish Liberal Democrats - A centrist party which promotes liberalism and federalism.

See also: Political parties in Scotland

Parties represented in the Welsh Assembly are:

• Welsh Labour Party - A centre-left party which promotes social democracy.
• Plaid Cymru - A centre-left party which promotes social democracy, democratic socialism and the creation of an independent Wales, free from the United Kingdom.
• Welsh Conservative Party - A centre-right party which promotes conservatism and strong unionism.
• Welsh Liberal Democrats - A centrist party which promotes liberalism and federalism.
• Wales Green Party - A left-wing party that is part of the Green Party of England and Wales and promotes green politics, more power being devolved to Wales and a universal basic income.

There are two main types of political parties in Northern Ireland; Republicans and Unionists. Republicans want Northern Ireland to leave the United Kingdom and join with the Republic of Ireland. Unionists want to keep Northern Ireland in the United Kingdom and there are parties who are open-minded about the issue. Parties represented in the Northern Ireland Assembly are:

• Democratic Unionist Party (DUP) - A right-wing Protestant party which strongly promotes British unionism.
• Sinn Fein (SF) - A left-wing Catholic party which promotes democratic socialism and Irish republicanism.
• Social Democratic and Labour Party (SDLP) - A centre-left party which promotes Irish republicanism and social democracy.
• Ulster Unionist Party (UUP) - A centre-right party which promotes British Unionism and conservatism. Allied to the UK Conservative Party.
• Alliance Party of Northern Ireland (APNI) - A centrist party which promotes liberalism and an end to sectarianism. It has no opinion on whether or not Northern Ireland should stay in or leave the United Kingdom.
• Green Party Northern Ireland (Green Party NI) - A centre-left party which promotes green politics. It has no opinion on whether or not Northern Ireland should stay in or leave the United Kingdom.
• People Before Profit (PBP) - A left-wing non-religious party.
• Traditional Unionist Voice (TUV) - A right-wing conservative and Eurosceptic party which strongly promotes British unionism.

• British National Party (BNP) - A far-right party which promotes policies of anti-immigration, right-wing populism and Third position economics.
• Northern Independence Party (NIP) - A party that supports northern England becoming an independent country.
• English Democrats - An England-only party that promotes federalism, conservatism and the separation of England from Scotland and Wales.
• Christian Party - A right-wing party that promotes Christian values and Conservative Christianity.
• Trade Unionist and Socialist Coalition (TUSC) - A left-wing alliance of parties including the Socialist Party of England and Wales, the Socialist Workers Party, Socialist Resistance and Solidarity.
• National Front - A far-right party that promotes fascism, British nationalism and a belief that the UK should only have White people living in it.
• Socialist Labour Party - A left-wing socialist and Eurosceptic party.
• Liberal Party - A centrist party that promotes liberalism and Euroscepticism.
• Christian Peoples Alliance - A centrist party that promotes Christian democracy.
• Mebyon Kernow (In English:Sons of Cornwall) - A centre-left party that wants to establish a Cornish Assembly.
• Progressive Unionist Party - A centre-left to left-wing political party only in Northern Ireland which supports British unionism.
• Socialist Alternative - A far-left Trotskyist party.
• Trust Party - A party that campaigned for trust in politicians in wake of the 2009 expenses scandal.
• The Official Monster Raving Loony Party - A party that promotes parties and highlights the stupidity of other more mainstream political parties.
• Scottish Socialist Party (SSP) - A Scotland-only left-wing party that promotes socialism, environmentalism, Scottish independence and Scottish republicanism.
• Alliance for Green Socialism - A left-wing socialist and environmentalist party.
• Social Democratic Party - A centre-left party which promotes social democracy.
• Pirate Party - A party which promotes reforms on copyright and privacy laws, as well as freedom of speech and freedom of expression.
• Communist Party of Britain - A far-left communist and Marxist–Leninist party.
• UK Independence Party - A right-wing to far-right party that promotes Euroscepticism and right-wing populism.