The Ilocos Region (Ilocano: Rehion/Deppaar ti Ilocos; Pangasinan: Rehiyon na Ilocos; Tagalog: Rehiyon ng Ilocos), designated as Region I, is an administrative region of the Philippines. Located in the northwestern section of Luzon, it is bordered by the Cordillera Administrative Region to the east, the Cagayan Valley to the northeast and southeast, Central Luzon to the south, and the South China Sea to the west.

The region comprises four provinces: Ilocos Norte, Ilocos Sur, La Union, and Pangasinan, along with one independent city, Dagupan City. The regional center is the City of San Fernando in La Union, which serves as the administrative hub of the region. The largest settlement in terms of population is San Carlos City in Pangasinan.

The 2020 Philippine Statistic Authority census reported that the major ethnolinguistic group composition of the region is predominantly made up of Ilocanos (58.3%), followed by Pangasinans (29.7%), Tagalogs (4.1%), and various Cordilleran (Igorot) indigenous groups.

The region is renowned for its rich natural and cultural attractions, featuring historic and UNESCO World Heritage sites, surfing spots, pristine beaches, island-hopping adventures, and the well-preserved Spanish baroque churches and colonial city of Vigan.

The region was originally inhabited by Negritos as early as 30,000 BC but over time, these early settlers were displaced by successive waves of Austronesian migrants who arrived via the region's narrow coastal areas using traditional boats known as balangay boat (referred to as biray or bilog in Ilocano). The migrations are explained by the widely accepted "Out of Taiwan" hypothesis, which posits that Neolithic Austronesian peoples migrated from Taiwan, forming the ancestral populations of contemporary Austronesians.

Austronesians are believed to have originated from Southern China or Taiwan and arrived in the Philippines through at least two major migration waves. The first wave, approximately 10,000 to 7,000 years ago, brought the ancestors of indigenous groups in the Cordillera Central mountain range. Subsequent migrations introduced additional Austronesian populations, along with agricultural practices, which eventually supplanted the languages of earlier inhabitants.

These Austronesian settlers included the Cordilleran (Igorot) groups, such as the Itneg (Tingguian) and the Isnag in the northern highlands, as well as the Kankanaey and Ibaloi in the southern highlands, who arrived during the first wave of migration. The second wave brought the Ilocanos, who settled in the northern coastal areas, alongside the Pangasinans, Bolinao and Zambals, who established communities in the southern and southwestern coastal zones.

With the establishment of commercial trading routes in Southeast Asia, settlements in the region flourished both culturally and economically through maritime trade.

The Ilocanos, known as Samtoy in pre-colonial times, actively traded goods and products with local and foreign merchants, including the Chinese and Japanese. One notable coastal trading post was Bee Gan (Chinese: 美岸; měi'àn; bí-gān), meaning "beautiful shore," which is now the city of Vigan. This site served as a significant hub for early Ilocano trade.

In the southern part of the region, the pre-colonial polity (panarian) of Caboloan was situated at the Agno River basin with Binalatongan as the capital, while Pangasinan was located at the delta and near the Lingayen Gulf, became a center for maritime trade. Gold mined from the Cordillera Mountain Range was transported along the Aringay-Tonglo-Balatok gold trail and traded in settlements like Agoo. At the time, Agoo's coastal shape made it an ideal harbor for foreign vessels.

This trade network connected the region to maritime routes spanning the Indian Ocean and the South China Sea. Goods exchanged included porcelain, silk (inabel), cotton, beeswax, honey, gemstones, beads, precious minerals, locally crafted burnáy (stoneware jars), and particularly gold.

Evidence of this trade has been uncovered in the Pangasinense port of Agoo, where porcelain and ceramic or pottery fragments were found during renovations of the Catholic church. These artifacts are now preserved in the Museo de Iloko. Japanese fishermen later established one of their first settlements in the Philippines in Agoo, introducing advanced fishing techniques and technologies to the local population.

Another notable aspect of the region's early history is the discovery of the Bolinao Skull, which dates to the 14th or 15th century and is associated with the early inhabitants of Pangasinan. The skull is particularly notable for its dental ornamentation, with teeth inlaid with gold. It was found alongside 67 other similarly adorned skulls and trade ware ceramics from the early Ming Dynasty. This discovery highlights the advanced aesthetic traditions, burial, trade practices, and social structures of ancient Filipino communities, offering valuable insights into the region's precolonial culture and history.

A year after Miguel López de Legazpi declared Manila the capital of the Philippines on June 24, 1571, Spanish colonization efforts expanded to Northern Luzon to "pacify the people."

Spanish conquistador Martín de Goiti began the conquest of Pangasinan and established several Spanish settlements between 1571 and 1573. By April 5, 1580, Pangasinan became an administrative and judicial district of the province, with Lingayen as its capital. However, its territorial boundaries were first delineated in 1611, with the area originating from the Spanish settlement in Manila through Pampanga.

On May 20, 1572, a year after Goiti's conquest, conquistadores led by Juan de Salcedo, the grandson of Legazpi, ventured northward with eight armed boats and 80 men. They sailed to Lingayen Gulf and landed at the mouth of the Agno River. In 1574, Limahong, a Chinese pirate, fled to Pangasinan after his fleet was driven away from Manila. Limahong attempted to establish a colony in Pangasinan but failed as an army led by Salcedo chased him out of the region after a seven-month siege.

Salcedo then continued his journey to Agoo, where he discovered a Japanese settlement and named it "El Puerto de Japón" after its conquest. He then reached Vigan on June 13, 1572, which had been a Chinese trading post from the Fujian province of China. In Vigan, he founded 'Villa Fernandina de Vigan' and made it the diocesan seat of Nueva Segovia in honor of King Philip II's son, Prince Ferdinand. Salcedo then proceeded to Laoag, Currimao, and Badoc, rounded the tip of Luzón, and continued to pacify the Bicol Region.

In 1574, Salcedo returned to Vigan with soldiers and Augustinian missionaries to initiate the evangelization of the Ilocos region. He established a Spanish city to control the neighboring territories and convert the native population to Catholicism.

As a reward for his services, Salcedo was granted the province of Ylocos, covering what is now Ilocos Norte, Ilocos Sur, Abra, La Union, and parts of Mountain Province, as his estate. He was also given the title Justicia Mayor de esta Provincia de Ylocos (Province Mayor of Ilocos). By the end of the 1700s, Ilocos had a population of 44,852 native families, 631 Spanish Filipino families, and 10,041 Chinese Filipino families.

Despite Spanish efforts, the Ilocanos in the northern parts of the region were less easily swayed and remained resistant to Spanish rule. These resentments led to several uprisings throughout the region's history, including the insurrections of Andrés Malong in 1660, Palaris of Pangasinan in 1762, Pedro Almazán in Ilocos Norte in 1661, Diego Silang and Gabriela Silang in 1764 and Basi Revolt in 1807. After the Basi Revolt, tensions culminated in the division of Ilocos into two provinces (Ilocos Norte and Ilocos Sur) on February 2, 1818. The Pangasinans in the south were the last to resist Spanish rule.

During the Philippine Revolution of 1896-1898, General Manuel Tinio allied with Emilio Aguinaldo to lead the revolution in Northern Luzon (Ilocos Siege), alongside General Francisco Makabulos. Makabulos led his forces to liberate Pangasinan and led revolutionaries in the Battle of Dagupan against the Spanish army. By August 1898, the revolutionaries had driven Spanish forces out of several towns, including Laoag, Ilocos Norte, marking a turning point in the revolution.

On June 12, 1898, General Emilio Aguinaldo proclaimed Philippine independence and became the first president of the Republic of the Philippines.

The American colonization of the Ilocos Region began following the conclusion of the Spanish-American War in 1898, when the Philippines was ceded to the United States under the Treaty of Paris. This marked a period of profound transformation for the region, which came under American colonial administration after the Philippine-American War (1899-1902).

On November 18, 1899, American forces landed in the Ilocos Region in pursuit of Emilio Aguinaldo, the leader of the Philippine resistance. While American troops swiftly occupied towns, they faced persistent resistance in the rural areas (barrios), where guerrilla forces led by Gen. Manuel Tinio continued the struggle. Tinio, a veteran of the 1896 Philippine Revolution against Spain, orchestrated a widespread guerrilla campaign, harassing American forces in the countryside.

One of the most iconic events during this period was the Battle of Tirad Pass on December 2, 1899. Gen. Gregorio del Pilar and his 60 soldiers faced over 300 troops of the U.S. 45th Infantry Division, led by Gen. Peyton C. March. Despite a valiant defense, the Filipinos ultimately lost their position, marking a significant, albeit symbolic, moment in the resistance against American forces.

The Philippine-American War officially ended in 1902, following years of intense conflict, with the establishment of a Filipino civilian government under American oversight. Civil governance was introduced in the Ilocos Region, as well as the rest of the Philippines, on July 1, 1901, with William H. Taft serving as the first Civil Governor. The position was later renamed Governor-General by the U.S. Congress on February 3, 1903. One of the most notable reforms was the establishment of a centralized public school system in 1901, using English as the medium of instruction. To address a shortage of educators, the colonial government deployed 600 American teachers known as the Thomasites.

By September 1902, public secondary schools had been established across the region, including institutions in Lingayen (Pangasinan), Vigan and Santa Maria (Ilocos Sur), Bauang, Bacnotan, and San Fernando (La Union), and Laoag and Dingras (Ilocos Norte) with several US Thomasites serving as educators. The Taft Commission per instructions of US President McKinley introduced free primary education, designed to prepare citizens for civic duties. Additionally, church lands were purchased and redistributed following the disestablishment of the Catholic Church, further signaling the shift in socio-political structures under American rule.

In 1901, several towns from Nueva Ecija including Balungao, Rosales, San Quintin, and Umingan were annexed to the province of Pangasinan. On November 30, 1903, additional municipalities from northern Zambales such as Agno, Alaminos, Anda, Bani, Bolinao, Burgos, Dasol, Infanta, and Mabini were transferred to Pangasinan. These towns, originally part of the homeland of the Sambal people, were reassigned due to their geographic distance from their original provincial capitals. Despite resistance from local communities, this decision has remained unchanged.

Under the Philippine Organic Act of 1902, the Ilocos Region experienced significant political, economic, and social changes. Infrastructure development flourished, with the construction of public schools, bridges, railways, airports, and ports, enhancing the region’s connectivity with other parts of the country.

However, these developments were accompanied by local unrest. Reports of war crimes, forced relocations, extrajudicial killings, and destruction of property by American forces fueled discontent among the population. While the introduction of modern governance and infrastructure brought progress, these human rights abuses left a lasting impact on the region's history.

American colonization ended on July 4, 1946 in WWII's aftermath gaining Philippines Independence from the United States.

The Japanese invasion of the Philippine Commonwealth began on December 8, 1941 during World War II, when Japan launched an attack on U.S. military installations and residential areas, following the attack on Pearl Harbor. Just two days later, the Japanese Kanno Detachment landed in Vigan, Ilocos Sur, aiming to secure airstrips for further military operations. Although initially unopposed, the landing was delayed by bad weather and American air attacks, which damaged Japanese ships and caused casualties. By December 11, the Japanese forces had successfully captured Vigan and dispatched additional troops to seize Laoag and its airfield. As American forces retreated, Lieutenan Gen. Masaharu Homma left a small garrison in Vigan and redirected the main forces to support operations at Lingayen Gulf.

By December 20, the combined forces of the Col. Kanno and Gen. Shizuichi Tanaka Detachments advanced south along Route 3. After overcoming Philippine defenses in Bacnotan, they reached San Fernando, La Union, by December 22. The Japanese 14th Army, commanded by Lieutenant General Masaharu Homma, had also landed at Lingayen Gulf, gaining control of key areas in Pangasinan and La Union. This marked the beginning of Japanese occupation of Northern Luzon, including the Lingayen Gulf region, which remained under Japanese control for three years, until it was recaptured by Allied forces in 1945.

During the occupation, the region was part of the Japanese-controlled puppet republic led by President José P. Laurel. The local population endured widespread atrocities committed by the Japanese Imperial Army, including gang rape, sexual slavery (comfort women), torture, and other human rights violations. These brutal acts sparked significant resistance movements across the region, with several guerrilla groups forming to oppose the Japanese occupation. One prominent leader of the local resistance was Captain Candonino Villalon Gaerlan, who led a successful ambush against Japanese forces in Candon, Ilocos Sur, symbolizing local defiance against the invaders.

By 1944, with the United States beginning its campaign to liberate the Philippines, the region became a crucial focal point for military operations. On October 20, 1944, the Allied forces initiated the liberation of the Philippines, setting the stage for the Battle of Lingayen Gulf in early 1945. On January 6, 1945, the U.S. Navy, supported by the Royal Australian Navy, began heavy bombardments of Japanese coastal defenses and infrastructure, lasting until January 8. Japanese kamikaze attacks targeted Allied vessels from January 7 to 9, but despite the damage, the U.S. Navy maintained control of the Gulf, securing it for the imminent invasion.

On January 9, known as S-Day, Gen. Douglas MacArthur and U.S. Army forces from the Sixth Army landed on a 25-mile beachhead between Lingayen and San Fabian. The landings, supported by over 800 ships and extensive air support, faced light resistance, as the Japanese had concentrated their defenses inland. By January 15, 1945, Allied forces had firmly secured the Lingayen Gulf region and began advancing into the heart of Luzon, paving the way for the liberation of Manila and the eventual defeat of Japanese forces in the Philippines.

The Ilocos region produced two presidents of the Republic of the Philippines within the first two decades after the recognition of Philippine independence: Elpidio Quirino and Ferdinand Marcos.

This period also marked a return of the tobacco industry to the Ilocos Region. Ever since the end of the tobacco monopoly, tobacco production had declined in the Ilocos as Filipinos started shifting from locally made cigars to foreign made cigarettes. But after reading a feature article series by Maximo Soliven which explained why Virginia tobacco would grow well on Ilocos soil, businessman Harry Stonehill was convinced to invest extensively in rebuilding the industry, establishing the Philippine Tobacco Flue-Curing and Redrying Corporation (PTFCRC) in 1951 and recruiting farmers from throughout Region 1 to produce tobacco. The following year, La Union Congressman Manuel T. Cases filed a bill to "limit the importation of foreign leaf tobacco," which was eventually signed by President Elpidio Quirino as Republic Act 698. This allowed Stonehill's investments to make a handsome profit, and the newly-rebuilt local industry to bloom. Stonehill was later deported a decade later, in the 1960s, for tax evasion and bribery of government officials, in what would later be called the Stonehill scandal, but the tobacco industry continued to grow.

Various human rights violations were documented in the Ilocos region during the Marcos martial law era, despite public perception that the region was supportive of Marcos' administration. In Ilocos Norte, various farmers from the towns of Vintar, Dumalneg, Solsona, Marcos, and Piddig were documented to have been tortured, and eight farmers in Bangui and three indigenous community members in Vintar were "salvaged" in 1984.

Ilocanos who were critical of Marcos' authoritarian rule included Roman Catholic Archbishop and Agoo, La Union native Antonio L. Mabutas, who spoke actively against the torture and killings of church workers. Other La Union natives who fought the dictatorship were student activists Romulo and Armando Palabay of San Fernando, La Union, whose torture and death in a military camp in Pampanga would lead them to being honored as martyrs in the fight against the dictatorship in the Philippines' Bantayog ng mga Bayani memorial.

In Ilocos Norte, one of the prominent victims of the Martial Law era who came from Laoag was Catholic layperson and social worker Purificacion Pedro, who volunteered in organizations protesting the Chico River Dam Project in the nearby Cordillera Central mountains. Wounded while visiting activist friends in Bataan, she was later killed by Marcos administration soldiers while recuperating in the hospital. Another prominent opponent of the martial law regime was human rights advocate and Bombo Radyo Laoag program host David Bueno, who worked with the Free Legal Assistance Group in Ilocos Norte during the later part of the Marcos administration and the early part of the succeeding Aquino administration. He would later be assassinated by motorcycle-riding men in fatigue uniforms on October 22, 1987 – part of a wave of assassinations which coincided with the 1986-87 coup d'état which tried to unseat the democratic government set up after the 1986 People Power Revolution. Both Bueno and Pedro were later honored among the first 65 people to have their names inscribed on the wall of remembrance of the Philippines' Bantayog ng mga Bayani, which honors the martyrs and heroes who fought the dictatorship, and Pedro was listed among Filipino Catholics nominated to be named Servant of God.

The integration of provinces into the Ilocos Region has evolved over time, shaped by political decisions aimed at administrative restructuring and cultural integration.

In 1973, Presidential Decree No. 1, issued by President Ferdinand Marcos, transferred the province of Pangasinan from Region III (Central Luzon) to Region I (Ilocos Region). This realignment was intended to strengthen Ilocano influence in Pangasinan, a province that had already experienced an influx of Ilocano settlers during the Spanish colonial era in the 19th century. Before this decree, Pangasinan had not been part of the Ilocos Region.

During the same period, the provinces of Abra, Mountain Province, and Benguet were also included in the Ilocos Region. These provinces, traditionally inhabited by indigenous groups, saw increased Ilocano migration. In particular, Abra had long been a destination for Ilocano settlers, dating back to the Spanish colonial period when it was part of the larger Ilocos Province, and later, Ilocos Sur. The inclusion of these provinces in the region was part of a broader strategy to expand Ilocano influence among the ethnic communities of the Cordilleras.

On July 15, 1987, President Corazon Aquino issued Executive Order No. 220, creating the Cordillera Administrative Region (CAR). This order transferred Abra, Mountain Province, and Benguet from the Ilocos Region to the newly established CAR, recognizing the Cordillera's indigenous peoples' unique cultural and historical identities.

As of today, the Ilocos Region consists of four provinces: Ilocos Norte, Ilocos Sur, La Union, and Pangasinan. Meanwhile, Abra, Mountain Province, and Benguet are part of the Cordillera Administrative Region.

The Ilocos region has produced 3 more Philippine Presidents in the years since the 1986 People Power revolution: Pangasinense Fidel V. Ramos, Gloria Macapagal Arroyo (Ilocano on mother's side), and Ferdinand Marcos' son Bongbong Marcos.

The southern parts of the region were severely hit by the 1990 Luzon earthquake. Five municipalities in La Union were affected: Agoo, Aringay, Caba, Santo Tomas, and Tubao with a combined population of 132,208. Many buildings, including the Agoo Municipal hall, the Museo de Iloko, the parish church of Aringay, and the Basilica Minore of our Lady of Charity, collapsed or were severely damaged. Sitio Nagpanauan in Aringay completely submerged when the sea level rose and the land collapsed during the earthquake. 100,000 families were displaced when two coastal villages sank due to liquefaction. The province suffered many casualties leaving 32 people dead. In Pangasinan, about 90 buildings in Dagupan were damaged, and about 20 collapsed. Some structures sustained damage because liquefaction caused buildings to sink as much as 1 metre (39 inches). The earthquake caused a decrease in the elevation of the city and several areas were flooded. The city suffered 64 casualties of which 47 survived and 17 died. Most injuries were sustained during stampedes at a university building and a theater.

The Ilocos Region, situated in the northwestern part of Luzon, Philippines, encompasses a total land area of 12,840.2 square kilometers. Of this area, 810,062 hectares are classified as alienable and disposable land, while 473,957 hectares are designated as forest land. The region is strategically positioned with direct access to international sea lanes and features diverse geographical landscapes. It is bordered by the South China Sea to the west and the Central Cordillera Mountain Range to the east. In contrast, Pangasinan occupies the northwestern section of the vast Central Luzon Plain, with the Zambales Mountains forming its natural western boundary.