Gregorio Aglipay Cruz y Labayán (Latin: Gregorius Aglipay Cruz; Filipino: Gregorio Labayan Aglipay Cruz; pronounced uhg-LEE-pahy; May 5, 1860 – September 1, 1940) was a Filipino former Roman Catholic priest and revolutionary during the Philippine Revolution and Philippine–American War who became the first head and leader of the Iglesia Filipina Independiente (IFI), the first-ever wholly Filipino-led independent Christian Church in the Philippines in the form of a nationalist church.

Known for inciting patriotic rebellion among the Filipino clergy during the Philippine Revolution and Philippine–American War, he was also a political activist who became acquainted with writer and labor leader Isabelo de los Reyes who would then start an independent Christian Filipino Church colloquially named after Aglipay in 1902 as a revolt against the Roman Catholic Church, which was the state religion of the Philippines at the time, due to the mistreatment of the Spanish friars towards the Filipinos. Contrary to popular belief, Aglipay did not join the IFI until one month from its proclamation by de los Reyes and the Unión Obrera Democrática.

Aglipay was previously excommunicated by Archbishop Bernardino Nozaleda y Villa of Manila in May 1899, upon the expressed permission of Pope Leo XIII, due to his involvement in revolutionary activities, despite his prior intercession and defense of some of the Spanish Roman Catholic clergy from liberal-nationalist Filipino revolutionaries. The Roman Catholic Church made attempts to bring Aglipay back to their fold, but failed. Aglipay joined Freemasonry in May 1918, a society excommunicated by the Roman Catholic Church. Aglipay married Pilar Jamias y Ver from Sarrat, Ilocos Norte in 1939 and then died one year later. Followers of Aglipay through the Church are sometimes colloquially referred to by their membership as Aglipayans.

Born in Batac, Ilocos Norte on May 5 and baptized on May 9, 1860 in the Roman Catholic Church, Aglipay personally preferred May 8 as the celebration for his date of birth. He was the third child of Pedro Aglipay y Cruz and Victoriana Labayán y Hilario and became an orphan at a young age who grew up in the care of relatives at the tobacco fields in the last volatile decades of the Spanish occupation in the Philippines. He bore deep grievances against the colonial Spanish government of the islands, stemming from abuses within the agricultural system. Arrested at age fourteen for failing to meet his quota as a tobacco-picking worker for a Spanish tobacco grower, he later moved to the country's capital of Manila in 1876 to study law under the tutelage of lawyer and private school owner Julian Carpio, with the financial help of his uncle Francisco del Amor Romas who was a menial employee of the Dominican Sisters School of Santa Catalina.

After two years of study under Carpio, Aglipay continued his studies at the Colegio de San Juan de Letran in 1878 for his third year as a working student, and later at the University of Santo Tomas in 1880 for his fourth year wherein he was an academic topnotcher. During his time in Santo Tomas, Aglipay met José Rizal, a senior medical student who used to be his fencing partner, and a newly-transferred Isabelo de los Reyes who also came from Letran. Aglipay obtained his pre-law Bachelor of Arts degree at Santo Tomas in 1881 and subsequently enrolled in law and theology in 1882, still at Santo Tomas. He then discontinued his law and theology studies at Santo Tomas and entered the Roman Catholic seminary in Vigan, Ilocos Sur in 1883 at age 23, as previously influenced by Rizal. He was ordained to the priesthood six years later on December 21, 1889, on the Feast of St. Thomas the Apostle, at the old Dominican Church in Intramuros, Manila and celebrated his first mass as an ordained Roman Catholic priest on January 1, 1890 at Santa Cruz Church, Manila.

Aglipay then began a career as an assistant priest to Spanish friars in various parishes around the main northern island of Luzon, notably in the Roman Catholic Archdiocese of Nueva Segovia. He later dropped Cruz in his surname and while serving in Victoria, Tarlac, Aglipay discreetly gave aid to the revolutionaries and employed thirty carpenters who in reality were revolutionists in touch with the Katipunan group. Aglipay then organized the said revolutionists and called their group Liwanag ("Light"), a local auxiliary of the Katipunan based in Victoria, Tarlac.

In 1896, a secret society, Katipunan, led by the Supremo, Andrés Bonifacio, was discovered by Spanish authorities. With Roman Catholicism as the state religion, Manila Archbishop Bernardino Nozaleda tasked Aglipay to confront the revolutionary leaders, offering them a level of autonomy in the future for the Philippines if they would end the rebellion. General Emilio Aguinaldo, in turn, sent Colonel Luciano San Miguel to Aglipay with the intention of getting him to join the rebellion. Aguinaldo convinced Aglipay, who appointed him as military chaplain (capellán castrense) of the revolutionary government sometime in May or June 1898, the first ever to be appointed as such in the Philippine Revolution.

Aglipay also later became a member of the Malolos Congress, the lone member coming from the religious sector, although he also represented his home province of Ilocos Norte, as well. On October 20, 1898, Aguinaldo elevated Aglipay to the post of Military Vicar General (Vicario General Castrense) of the revolutionaries, a position that made him head of all military chaplains in the revolution. In the course of Aglipay's journey to the north, the Philippine–American War started at the conclusion of the Spanish–American War. Aglipay interpreted his appointment as Vicar General as making him Ecclesiastical Superior to all native Filipino priests, who as such should all be appointed military chaplains for the duration of the war.