Juan José Nieto Gil (24 June 1804 – 16 July 1866) was a Colombian politician, Army general and writer. A Liberal party caudillo of Cartagena, he served interimly as Governor of the Province of Cartagena, and was later elected President of the Sovereign State of Bolívar from 1859 to 1864. In 1861, during the Colombian Civil War, he fought on the side of the Liberal rebels against the Administration of President Mariano Ospina Rodríguez, and acting in rebellion proclaimed himself President of the Granadine Confederation in his right as the Presidential Designate, relinquishing power four months later to the Liberal leader, General Tomás Cipriano de Mosquera y Arboleda, who led a successful coup d'état against the Conservative Government in Bogotá.