centrist political party of Switzerland. With the Christian Democratic People's Party, the Social Democratic Party (Social Democratic Party of Switzerland), and the Swiss People's Party, the Radical Democratic Party has governed Switzerland as part of a grand coalition since 1959.

The Radical Democratic Party, sometimes known as the Free-Thinking Democratic Party, traces its roots to the movement that gave rise in 1848 to the Swiss Confederation and to the country's first constitution. From 1848 to the end of the 19th century, when it was known as the Liberal Party, it dominated Swiss politics. In 1876 a Radical Democratic faction was formally established in the Swiss legislature, and in 1894 the party was officially founded. The introduction of proportional representation for national elections in the 20th century reduced its strength, but it continued to play a leading role in Swiss politics throughout the century. Since its founding the Radical Democratic Party has supported a strong federal government and a market economy, but at the same time, it has been an advocate for the rights of local government and of minority groups.

Since 1959 the party has been represented by two of the seven members of the Federal Council, the Swiss government's executive branch. It has long been among the strongest of the political forces in the Swiss government, and it was the country's largest party from 1983 through 1995, winning about one-fourth of the total vote. Even during the 1990s, when the party fell to third place and when there was a shift in the electorate in favour of more restrictive immigration and social policies, the party retained a major role in the country's political life.