The Siege of Paysandú occurred during the Uruguayan War, during which the Brazilian Armed Forces, under Marquis of Tamandaré and Colorado forces under Venancio Flores attempted to capture the city of Paysandú in Uruguay from its Uruguayan Army defenders. The siege lasted from 3 December 1864 until 2 January 1865, finally ending when the Brazilian and Colorado forces successfully conquered the town.