Juan de Arregui y Gutiérrez (1656–1736) was a Spanish-American prelate of the Roman Catholic Church and a colonial administrator who served in the Viceroyalty of Peru. He is historically recognized for his dual roles as the Bishop of Buenos Aires and the temporary Governor of Paraguay.
Born in Buenos Aires, Arregui entered the Order of Friars Minor (Franciscans) and pursued a career within the ecclesiastical hierarchy of the Spanish colonies. On November 22, 1730, he was appointed Bishop of Buenos Aires by Pope Clement XII and was consecrated in 1731.
Arregui's involvement in secular politics occurred during the Second Revolt of the Comuneros in Paraguay, a period of significant social and political unrest against the colonial authorities and the Jesuit missions. In 1733, while traveling to Asunción to perform episcopal duties, he arrived shortly after the death of Governor Agustín de Ruiloba, who had been killed in a skirmish with the comunero rebels.
Due to the vacancy in leadership and the pressure from the insurgent local council (cabildo), Arregui was proclaimed Governor of Paraguay in July 1733. His appointment was initially seen as a compromise to stabilize the region; however, his brief tenure was complicated by the intense factionalism of the revolt. Arregui served as governor for approximately seven months before resigning the post in early 1734 to return to his diocese in Buenos Aires.
He continued to serve as the Bishop of Buenos Aires until his death on December 19, 1736. His life remains a point of study for historians examining the intersection of church and state during the civil conflicts of 18th-century Spanish South America.