Joaquín de Montserrat, 1st Marquess of Cruillas (June 26, 1700 – November 21, 1771) was Spanish viceroy of New Spain, from October 6, 1760 to August 24, 1766.

Viceroy Montserrat took economy measures, ordered the collection of back taxes, and prohibited hoarding of foodstuffs and merchandise.

Other disasters during Montserrat's term of office included a major flood in Guanajuato that paralyzed the operation of the silver mines (April, 1762), and another epidemic (of "fever") that caused many deaths (1763).

He also had to send military assistance to Sonora, where a revolt of Pimas and Seris had broken out against their maltreatment by the Spanish colonists.

In January, 1762, after the accession of Charles III to the Spanish throne, Spain was again at war with the Kingdom of Great Britain.

Spain received Louisiana and regained Havana and Manila from the British, but ceded Florida to Great Britain, as well as the right of settlement and timber-harvesting in modern-day Belize.

In 1764, he organized the postal service, sent aid to Cuba, and continued work on the drainage system of Mexico City.

The Crown named José de Gálvez as visitador (inspector), with full powers to reform the administration and introduce new economic ideas.