The Libertador General San Martín Bridge (Spanish: Puente Libertador General San Martín) is a cantilever road bridge that crosses the Uruguay River and joins Argentina and Uruguay. It runs between Puerto Unzué, near Gualeguaychú, Entre Ríos Province, Argentina, and Fray Bentos, Río Negro Department, Uruguay, with a total length of 5,366 meters (3.334 miles) (4,220 meters (13,850 feet) in Argentine jurisdiction and 1,146 meters (3,760 feet) in Uruguayan territory), including the bridge and accesses embankments.

Studies for the construction of a bridge over the Uruguay River were started in 1960 by a joint commission, which decided that the best place for it would be between Puerto Unzué and Fray Bentos. In 1967 the two countries signed an agreement ratifying the location, and in 1972 the construction contract was awarded to the International Bridge Consortium (Consorcio Puente Internacional), setting the cost at $ 21.7 million, then adjusted upwards.

The bridge is named after José de San Martín, a major figure in the struggle for independence in Argentina, Chile and Peru. It was officially inaugurated on September 16, 1976. It was opened for public use and the next day it started functioning under a toll regime.