SDP–Liberal Alliance in the context of "Social Democratic Party (UK)"

The Liberal Democrats, colloquially known as the Lib Dems, is one of the major political parties in the United Kingdom. Ideologically adhering to liberalism, it was founded in 1988. The party is based at Liberal Democrat Headquarters, which since September 2025 has been based at Buckingham Gate, in the Westminster area of Central London. The party's leader is Ed Davey. It is the third-largest party in the United Kingdom, with 72 members of Parliament (MPs) in the House of Commons. It has 75 members of the House of Lords, 5 in the Scottish Parliament, 1 in the Welsh Senedd, and around 3,200 local council seats. The party holds a twice yearly Liberal Democrat Conference, at which policy is formulated. In contrast to its main opponents, the Lib Dems grant all members attending Conference the right to vote on policy, under a one member, one vote system. As well as voting in the Conference Hall, the party allows its members to vote online for its policies and leadership elections. Members are also free to join organisations representing strands of party thinking, such as Liberal Reform and Social Liberal Forum, and for those under 30 years, Young Liberals.

In 1981, an electoral alliance was established between the Liberal Party, a group which descended from the 18th-century Whigs, and the Social Democratic Party (SDP), a splinter group from the Labour Party. In 1988, the parties merged as the Social and Liberal Democrats, adopting their present name a year later. Under the leaderships of Paddy Ashdown and Charles Kennedy, the party grew in the 1990s and 2000s, focusing its campaigns on specific seats and retained the third-largest party status in the House of Commons, although with significantly more seats than the predecessor Liberal Party. In the 1997 election, the Liberal Democrats doubled their seat count to 46. In 2010, under Nick Clegg's leadership, the Lib Dems were junior partners in the Conservative-led coalition government, in which Clegg served as deputy prime minister. Though it allowed the party to implement some of its policies, the coalition damaged its electoral standing; it lost 48 of its 56 MPs at the 2015 general election, which relegated it to fourth-largest party in the House of Commons. Under the leaderships of Tim Farron, Vince Cable and Jo Swinson, the party refocused as a pro-Europeanist party opposing Brexit. In the 2019 general election, the party garnered 11.5% of the vote on an anti-Brexit platform, but this did not translate into seat gains. However, the party's success was renewed under the leadership of Ed Davey, winning hundreds of councillors and 72 MPs in the 2024 general election, its highest result since 1923, and resuming its status as the third largest party in the House of Commons.

Charles Peter Kennedy (25 November 1959 – 1 June 2015) was a British politician who served as Leader of the Liberal Democrats from 1999 to 2006, and was the Member of Parliament (MP) for Ross, Skye and Lochaber from 1983 to 2015.

Kennedy was elected to the House of Commons in 1983 as a member of the Social Democratic Party, and after the SDP–Liberal Alliance merged into the Liberal Democrats, became the party's president. Following the resignation of Paddy Ashdown in August 1999, Kennedy became the party's leader. He led the party in the 2001 and 2005 general elections, increasing its number of seats in the House of Commons to their highest level since 1923, led his party's opposition to the Iraq War, and broadly positioned the party to the left of New Labour. A charismatic and affable speaker in public, he appeared extensively on television during his leadership.

In the United Kingdom, the word liberalism can have any of several meanings. Scholars primarily use the term to refer to classical liberalism. The term can also mean economic liberalism, social liberalism or political liberalism. It can simply refer to the ideology and practises of the historic Liberal Party (1859–1988), or in the contemporary context, of the Liberal Democrats: the successor to the old Liberal Party after it merged with the centrist Social Democratic Party (SDP), with which the Liberals had been in a Britain-wide electoral alliance since shortly after the latter was formed.

Liberalism can occasionally have the imported American meaning, especially since 2016; however, the pejorative connotation is much weaker in the UK than in the US, and social liberals from both the left and right wing continue to use liberal and illiberal to describe themselves and their opponents, respectively.