The Constitutional Democratic Party (Russian: Конституцио́нно-демократи́ческая па́ртия, romanized: Konstitutsionno-demokraticheskaya partiya, K-D), also called Constitutional Democrats and formally the Party of People's Freedom (Russian: Па́ртия Наро́дной Свобо́ды), was a centrist, liberal political party in the Russian Empire that promoted Western constitutional monarchy — among other policies — and attracted a base ranging from moderate conservatives to mild socialists. Party members were called Kadets (or Cadets) from the abbreviation K-D of the party name. Konstantin Kavelin's and Boris Chicherin's writings formed the theoretical basis of the party's platform. Historian Pavel Miliukov was the party's leader throughout its existence.

The Kadets' base of support were primarily intellectuals and professionals; university professors and lawyers were particularly prominent within the party. Many Kadet party members were veterans of the zemstvo, local councils. The Constitutional Democratic Party formed from the merger of several liberal groupings, namely the Union of Liberation, the Union of Zemstvo Constitutionalists and the Union of Unions as well as the organization of bourgeois professionals and intellectuals, including teachers, lawyers, writers, physicians and engineers.

The Kadets' liberal economic program favored the workers' right to an eight-hour day and the right to take strike action. The Kadets "were unwaveringly committed to full citizenship for all of Russia's minorities" and supported Jewish emancipation. The party drew significant support from Jews and Volga Germans and a significant number of each group were active party members.