The National Democratic Party (Spanish: Partido Demócrata Nacional, PDN) was an Argentine conservative party created in 1931 which disappeared after 1955. It was generally known simply as Conservative Party (Spanish: Partido Conservador).
Along the Antipersonalist Radical Civic Union (UCR-A) and the Independent Socialist Party (PSI) it was a part of the Concordancia, a coalition government that ruled between 1932 and 1943, a period of Argentine History known as the "Infamous Decade", characterised by massive voter fraud.
Among its leading figures were Robustiano Patrón Costas, Julio Argentino Pascual Roca, Manuel Fresco and Rodolfo Moreno. Ramón S. Castillo, Vice-President to Roberto María Ortiz, who went to serve as acting President between 1940 and 1942, and later as President until June 4, 1943, was a member of this party.
After the "Revolución Libertadora" (1955–1958), the military uprising which overthrew Juan Perón, the PDN fragmented into various parties such as the "Partido Conservador Popular" (PCP), the "Partido Demócrata" and the "Partido Demócrata de Centro".