Francisco Antonio de Agurto y Salcedo Medrano Zúñiga, 1st Marquess of Gastañaga (1640 – 2 November 1702) was a Spanish nobleman, Knight of the Order of Alcantara, of His Majesty's Supreme War Council, General Field Marshal of the Netherlands, Governor and Captain General of the Spanish Netherlands and Viceroy of Catalonia, of Basque origin.

[2] Francisco Antonio de Agurto succeeded his brother Juan Miguel in the majorat of his house, due to the latter's death without legitimate offspring.

In 1682, he was appointed General Field Marshal of Flanders and in the same year, he hosted Mary II of England, Princess of Orange during her visit to Brussels.

A royal proclamation was made, in the form of a patent, appointing Francisco Antonio de Agurto, 1st Marquess of Gastañaga as Governor and Captain General of the Netherlands, with all the clauses, prerogatives, and authority enjoyed by his predecessor, in recognition of his great merits, distinguished services, complete satisfaction, and the trust that His Majesty had in him.

[4][5] The Marquess Francisco Antonio de Agurto Salcedo Medrano Zuñiga took command of the Army of Flanders during his time in Government over the Habsburg Netherlands.

He used the initial moments of his administration to visit Brabant and Flanders and focused on strengthening fortifications and reviewing pending legal matters within the country.

Gastañaga was alerted to an imminent French offensive and attempted to arrange military collaboration with the Prince of Waldeck, commander-in-chief of the troops in the United Provinces.

In 1689, Antonio requested the sole-director of the first Royal Military and Mathematics Academy of Brussels, Sebastián Fernández de Medrano, to accompany him, being Master of Camp General, on the journey and visit, as Sebastian himself wrote, "to see some of Germany's places, which were Cologne, Bonn, Kolbenz and Trier," where they met the Elector of Trier, Johann Hugo von Orsbeck.

In a bold envelopment, Marshal Luxembourg, commanding a French army, inflicted a severe defeat on an Allied force led by Prince Waldeck.

[6] In February 1691, Gastañaga set off for The Hague, where he met with the electors of Bavaria and Brandenburg, the landgrave of Hesse-Cassel, and various allied army commanders, in the presence of King William III of England, to agree on joint actions against the French offensive.

He was accused of not taking the necessary measures for defense while assuring William III that there was no danger, misleading him about the number of troops that made up the garrison.

Perhaps disillusioned by the difficult situation in the southern provinces, the Marquis soon recognized, during the War of the Grand Alliance (1688-1697), that the Spanish Netherlands had become a bastion for Germany, Italy, and the Dutch Republic against the armies of Louis XIV.

[6] On 1 March 1687, Don Sebastian Fernandez de Medrano, the sole-director of the first Modern Royal Military and Mathematics Academy of Brussels in Europe (Brussels, 1675-1706) dedicated his academic book: "El ingeniero: primera parte, de la moderna architectura militar (1687)" to the 1st Marquess of Gastañaga, whom he chose as the patron and protector of his Royal Military and Mathematics Academy:[9] "To the Most Excellent Lord Marquis of Gastanaga (D. Francisco de Agurto Salcedo Medrano Zúñiga), Knight of the Military Order of Alcantara, Governor and Captain General of the Low Countries.

My humble works testify to it, as after the practical artilleryman and geography, this third one seeks the same sacredness as the others, confident that I will find in Your Excellency's benevolence the welcome that Flavius Josephus' writings received from Emperor Titus, and not the disdain shown by Antigonus, King of Macedonia, to a philosopher for dedicating a book of justice to him (at a time when he was deposing kings and sovereigns).

And since human malice does not allow for its preservation without the power of arms, and the force of arms obliges (those who wish to live securely while preserving it) to close and fortify their defenses, there would be no reason, Most Excellent Lord, for this treatise on Modern Fortification to seek any other shade than that of Your Excellency, who, being so well-versed in its theory and experienced in its practice, can accurately judge the errors it may contain (which, being my work, it might have).

Here, my pen would have plenty of space to expand upon the glories that Your Excellency has achieved, from the position of Captain of Spanish Infantry to that of most deserving Governor of these states, which you possess today with such general applause.

He began a new royal chapel of Saint Joseph in Waterloo in 1687 an attempt to curry favour with the court, but was recalled to Madrid for his failure to hold Mons.

A Latin inscription, still visible on the pediment of the ‘Pronaos’ (porch) refers to this occasion: "To our great and good God, and dedicated to Saints Joseph and Anne, for the succession desired by the Catholic Lords to Charles II, King of Spain and the Indies and Prince of Belgium, Francisco Antonio de Agurto Marquess of Gastañaga offers this chapel and lays its foundation stone with a prayer for all eternity".

In the inside of the dome, numerous commemorative plates indicate the names of officers of the allied armies who were killed during the Mount-St-Jean’s battle of Waterloo on June 18th 1815.

The four main panels represent the Sermon on the Mount, the miraculous draught of fishes, the Samaritan woman and Jesus welcoming the children.

On the other hand, the kingdom owed him salaries from his time as Governor, a debt that, as a special favor to him, was recognized by Felipe V, who ordered the outstanding amount to be paid.