The Constitution of the Argentine Nation (Spanish: Constitución de la Nación Argentina) is the basic governing document of Argentina, and the primary source of existing law in Argentina. Its first version was written in 1853 by a constitutional assembly which gathered in Santa Fe; the doctrinal basis was taken in part from the United States Constitution. It was then reformed in 1860, 1866, 1898, 1949, 1957 (which mainly repealed the 1949 reform), and the current version is the reformed text of 1994. It's the seventh oldest national constitution currently in effect being ratified on 1 May 1853.

The Argentine Constitution consists of a preamble and two normative parts:

The following international human rights instruments —treaties and declarations— also have constitutional status by virtue of article 75 paragraph 22:

The first attempt to divide political power in Argentina was during the government created after the May Revolution (Spanish: Revolución de Mayo): the Primera Junta could not create new taxes without the Cabildo's authorization.

Many revolutionary leaders, led by Mariano Moreno, wanted to declare independence immediately and create a constitution in order to build an independent state. In October 1811, the Junta Grande, which succeeded the Primera Junta, enacted the Regulation for the Division of Power, but it was not accepted by the executive power. Nevertheless, the freedom of press and the Decree on Individual Security were accepted by November. In 1813, the General Constitutional Assembly was intended to declare a constitution but it could only declare the freedom for slaves' sons.

In 1819 and 1826 were declared two constitutions that eventually failed because of the disagreement between Federalists and Unitarians. Many other constitutional pacts existed between 1820 and 1853 (when the current Argentine Constitution was enacted). The most important of them are: the Treaty of Pilar (1820), the Treaty of the Cuadrilátero (1822), the Federal Pact (1831), the Palermo Protocol (1852), and the Treaty of San Nicolás (1852).

The Federal Pact urged all the provinces to call a General Federal Congress, however this would have limited Juan Manuel de Rosas's power who was the most powerful province governor, so the Congress was never called. When Rosas was defeated, in 1852, the Treaty of San Nicolás finally called the Constitutional Congress that, in Santa Fe, on 1 May 1853, swore to make effective the federal Constitution. Consequently, the Province of Buenos Aires left the Argentine Confederation until 1859.

The first constitutional amendment to the original 1853 text occurred in 1860 after Buenos Aires rejoined the Argentine Confederation. It consisted of changes to many of the original articles. One of the major changes was the renaming of the state: according to the reform, the country would be officially named República Argentina ("Argentine Republic") and, for legal purposes, Nación Argentina ("Argentine Nation"), replacing the older "Argentine Confederation" in all articles of the constitution. Another important inclusion was the constitutional recognition of Buenos Aires' exclusive rights guaranteed by the Treaty of San Nicolás.