The Hay-Bunau Varilla Treaty, Cross-Isthmus Canal Convention or Isthmian Canal Convention was an international agreement entered into between the governments of Panama and the United States for the construction of the Panama Canal.

The treaty was signed on November 18, 1903, by Philippe Bunau-Varilla, representative of the government of Panama, and John Milton Hay, representative of the United States, a few days after Panama's separation from Colombia. Said treaty, in addition to its main objective, contained clauses that in practice placed Panama under US protection to guarantee its separation, and avoid military actions by Colombia in response to its secession. In addition, it allowed the establishment of American rule over a strip 16 km (10 miles) wide, over which the Panama Canal would pass and which was called the Panama Canal Zone.

This treaty was valid until October 1, 1979, the date on which the Torrijos-Carter treaties came into force, ending the US presence and administration in the Panama Canal.

Panama had been an integral part of all forms of political and territorial organization that the Republic of Colombia had from 1831 to 1903, with around seventeen attempts at secession and two separations completed during the century. Panama; the Thousand Days War, which caused great human and material losses in the isthmus; the old autonomist pretensions of the Panamanian political class[3]​ and the rejection of the Herrán-Hay treaty by the Colombian congress. The Panamanian separatists were supported by the government of US President Theodore Roosevelt, for which the construction of the Panama Canal was a geostrategic objective.[4][5][6]​.

On the afternoon of November 4, 1903, the provisional government formally proclaimed the Republic of Panama. On November 6, the US government, through Secretary of State John M. Hay, made the de facto recognition of the new nation, through a telegram sent to the consul "Consul (foreign service)") of Panama.

While the new country was organizing institutionally, Philippe Bunau-Varilla, as a reward for his help in the insurrection, had been insisting on his appointment as Plenipotentiary Minister of Panama in the United States, since he had fulfilled his part in the pact agreed with Manuel Amador Guerrero (later the first elected president of Panama) in New York, on October 20, 1903, when the separation of Panama was in the preparatory phase.