The Buenos Aires and Rosario Railway (BA&R) was a British-owned railway company that built and operated a 5 ft 6 in (1,676 mm) broad gauge railway network in Argentina, where it was known as the Ferrocarril Buenos Aires y Rosario.
On 10 September 1870 the Buenos Aires Province awarded Guillermo E. Matti the concession to build a line from Buenos Aires to Campana, a port on the River Paraná. In April 1874 Matti formed the Compañia del Ferrocarril a Campana (in English: Buenos Aires and Campana Railway), the line was opened on 8 April 1876, and later a further concession was granted to the company for an extension to Zárate and Rosario. On 9 May 1885 the company changed its name to the BA&R. The first train between Buenos Aires and Rosario (North Station) ran on 1 February 1886, a momentous occasion because until this time railway developments in Argentina had centred around the cities of Buenos Aires and Rosario but now, for the first time, the cities were linked.
From this point on the rate of expansion of the company increased and from Rosario the line was extended to Gálvez (October 1886), Rafaela (March 1887), Sunchales (June 1887), La Banda (September 1890) and Tucumán (February 1891). Branch lines were built from San Lorenzo to Puerto San Martín and Puerto Cerana (1889), from Bernardo de Irigoyen to Santa Fe (1892), Gálvez to San Francisco (1890), from La Banda to Santiago del Estero (February 1891), and from Cevil Pozo to El Chañar (1896). On 9 August 1890 the company acquired a 22 km line from Coghlan junction, on the main line, to Tigre, which put the company in direct competition with the Central Argentine Railway (CA).
By the mid 1890s the BA&R was the second largest British-owned railway company in Argentina and was effectively challenging the CA’s monopoly of the north-west of the country. On 20 September 1900 the BA&R bought the 490 km metre gauge rail network built by the British-owned company Santa Fe and Córdoba Great Southern Railway (SF&CGS). The sale included a concession already granted to the SF&CGS for the extension of their network from La Carlota to Río Cuarto which the BA&R opened on 26 March 1902.
In 1908 the company was taken over by the Central Argentine Railway.