Auguste Dreyfus (28 June 1827 – 25 May 1897) was a French businessman who made his fortune by financing the Peruvian trade in guano.

[a] Dreyfus joined a small textile trading firm set up by three of his elder brothers and moved to Lima, Peru to act as their local representative.

The Peruvian government let Dreyfus act as their agent in managing their existing debt and floating new loans used for railway construction.

A lengthy series of lawsuits followed between the creditors whose loans were secured by guano deposits and the governments of Peru and Chile.

[4] Auguste began trading in guano, and quickly became wealthy through careful attention to the fluctuations in the global demand for the commodity.

[6] Leon Dreyfus, who had moved to Peru and made influential connections, became a partner on 19 January 1866 and remained associated with Auguste until 1869.

[6] The government of Peru had been exploiting their guano reserves on a consignment system, in which the state paid contractors to extract, transport and sell it on a cost-plus basis.

[7] On 5 July 1869 the government cancelled all consignment arrangements and granted Dreyfus Frères the exclusive right to sell up to two million tons of guano in Europe.

[12] A private addendum to the contract stipulated that Dreyfus's choice of banker would handle Peruvian financial affairs in London.

[14] The income provided by the Dreyfus contract was absorbed in payments to an expanding civil service and armed forces.

[15] Rather than reduce debts or invest in urgently needed schools or irrigation projects, Pierola used the income from the contract as collateral for additional loans, which President José Balta used for an ambitious plan promoted by Henry Meiggs to build railways in the mountainous Andes country.

[16] Peru had hoped to sell almost £37 million of the 1872 bonds, but investors were concerned about the country's ability to serve its soaring debts, and there were rumors that the guano supplies were running out.

[19] Pardo reduced the size of the army by three-quarters and canceled two orders for battleships from Britain, but continued the railway construction program.

[21] Dreyfus now began suffering from the declining quality of the remaining guano and from competition with artificial fertilizer manufactured in Germany.

[23] Manuel Pardo's presidency ended among growing economic problems compounded by civil unrest and a brewing crisis with Chile.

[25] One of Prado's first acts was to travel to London, where on 7 June 1876 he signed an agreement by which Peru sold 1,900,000 tons of guano to Raphael's consortium.

[26] The competing Peruvian Guano Company was handicapped by terms that favored Peru, and until 1879 was not allowed to sell at competitive prices.

[27] By late 1879 the Peruvian government still owed Dreyfus £4 million, secured by the country's remaining reserves of guano.

[28] In the years that followed Dreyfus, the bondholders of the Peruvian Guano Company and other creditors, sometimes backed by the French or British governments, made conflicting claims against Chile and Peru with limited success.

[34] Dreyfus chose Waldeck-Rousseau, a prominent Republican who had been Minister of the Interior in 1884, as his advocate in his case against the Société Générale, formerly his partner.

[3] His wife's brothers, Charles and Frederick Bergman, won a contract in August 1869 to build and run dock facilities in the port of Callao, which they sold to the Société Générale in 1874.

Louis Dreyfus (1874–1965), was successively authorized by decree of 12 August 1885 to call himself Dreyfus-Gonzalez de Andia, then in 1925 by Alfonso XIII of Spain, to assume – contrary to the Spanish noble usage – the title of his mother, who died a year before, and finally, by decree of 26 July 1935, to remove Dreyfus from his name.

[2] In June 1888 Dreyfus bought the domain of the Château de Pontchartrain from Count Guido Henckel von Donnersmarck.

[48] In June 1896 the Dreyfus-Gonzalez collection was sold at public auction in Paris, and included among other valuables four candelabra called "the sirens and garlands of leaves" (c. 1783–1784) attributed to the great bronze sculptor François Remond and coming from a series of six that were part of the furniture of the Parisian hotel of the second Duke of Praslin (1735–1791), which were acquired by the Duke of Hamilton.