The Pact of San José de Flores was a treaty signed between the Argentine Confederation and the State of Buenos Aires on November 11, 1859, on the aftermath of the Battle of Cepeda. It established guidelines for the entry of the latter into the Confederation, and Buenos Aires' acceptance of the Argentine Constitution of 1853.

The State of Buenos Aires was a secessionist republic resulting from the overthrow of the Argentine Confederation government in the Province of Buenos Aires on September 11, 1852. The State of Buenos Aires was never recognized by the Confederation; it remained, however, independent under its own government and constitution. Buenos Aires rejoined the Argentine Confederation after the former's victory at the Battle of Pavón in 1861.