The Assembly of Year XIII (Spanish: Asamblea del Año XIII) was a meeting called by the Second Triumvirate governing the young republic of the United Provinces of the Río de la Plata (today's Uruguay and parts of Argentina and Bolivia) on October 1812.
One of the objectives of the assembly was to define an institutional government system for the republic. Without the presence of representatives from some of the provinces (such as the Oriental Province), it was inaugurated on January 31, 1813 (hence the name). At the same time, it was to proclaim independence from Spain, and write the first constitution of the young state.
During the assembly, different interests delayed the declaration of independence, but a number of common points were successfully established: