José Ambrosio Brunetti y Gayeso, 15th Duke of Arcos GE (6 February 1839 – 5 September 1928) was a Spanish aristocrat and diplomat who served as Minister Plenipotentiary in Bolivia, Uruguay, Chile, Mexico, the United States and Belgium, and ambassador to Italy and Russia.

He was also an important benefactor of the Prado Museum, to which he made a posthumous bequest of ten paintings, including Young Man with a Feather Hat, by Pieter Hermansz Verelst.

He was the son of María Josefa Gayoso y Téllez-Girón and Count Lázaro Brunetti (1781–1838), who was originally from Massa and who served Austrian ambassador in Madrid during most of the reign of King Ferdinand VII.

Brunetti, nephew of the 12th Duke of Osuna, ran as heir to the historic duchy of Arcos, but other family members preceded him in formally requesting succession to the title before the Ministry of Grace and Justice: the Marquess of Castillo del Valle de Sidueña and the Marquess of Alventos, descendants of minor branches of the Ponce de León, the original lineage of the House of Arcos.

Alventos managed to obtain a Royal Charter of Succession in the title in 1886, but it was immediately suspended due to the lawsuit that he had continued with Brunetti since 1884, and which was resolved in his favor by a ruling in January 1892.

[15] Her parents opposed her courtship with Count Brunetti, a young diplomat without fortune, and although they also disapproved of his main rival, a naval officer who would eventually become the famous Admiral George Dewey, they preferred him because he was American.

After leaving for successive destinations in Latin America, and after succeeding to the dukedom, in 1895, almost two decades later, her father withdrew his veto, and the couple married in October 1895 at the Lowerys' summer home in New London, Connecticut.