The Rosario and Puerto Belgrano Railway was a French-owned railway company which operated a 5 ft 6 in broad gauge, 5 ft 6 in, single track line between the cities of Rosario and Puerto Belgrano in Argentina. Puerto Belgrano, near the city of Bahía Blanca in Buenos Aires Province, is the main naval base in Argentina. The original idea behind the building of the railway was to link points that were closer to either Rosario or Bahía Blanca than they were to Buenos Aires, thereby taking traffic from the British-owned companies BA Great Southern and BA Western railways.

Rosario is the largest city in the central Argentine province of Santa Fe. The city, located 300 km (186 mi) northwest of Buenos Aires on the west bank of the Paraná River, is the third-most populous city in the country, and is also the most populous city in Argentina that is not a capital. With a growing and important metropolitan area, Greater Rosario has an estimated population of 1,750,000 as of 2020. One of its main attractions includes the neoclassical, Art Nouveau, and Art Deco architecture that has been preserved in hundreds of residences, houses and public buildings.