Lal-lo, officially the Municipality of Lal-Lo (Ibanag: Ili nat Lal-lo; Ilocano: Ili ti Lal-lo; Tagalog: Bayan ng Lal-lo), is a municipality in the province of Cagayan, Philippines. According to the 2020 census, it had a population of 48,733 people.

During the Spanish colonial period, Lal-lo was known as Ciudad de Nueva Segovia and was the seat of the Diocese of Nueva Segovia before it was moved to Vigan in Ilocos Sur. It is currently under efforts to regain its Spanish-era city status.

Recently, the provincial government of Cagayan through the leadership of Governor Manuel Mamba planned to make Lal-lo the provincial capital of Cagayan again.

The Northern Cagayan International Airport in southern Lal-lo was constructed to support both the Cagayan Special Economic Zone in northern Cagayan and to serve seaborne traffic through Port Irene. The airport project involved the construction of a 2,200 metres (7,200 ft) runway with a width of 45 miles (72 km), following the standards of the International Civil Aviation Organization. The international airport accommodates large aircraft such as the Airbus A319-100 and Boeing regional jets of comparable size. Royal Air Philippines offers service twice weekly using BAe146 aircraft.

Lal-lo is 81 kilometres (50 mi) from Tuguegarao and 562 kilometres (349 mi) from Manila.

Lal-lo means "twisting two strands to make a rope", or may also refer to the strong river current as it is located along Cagayan River, the longest and largest river in the Philippines.

In Fr. Jose Bugarin's Ibanag dictionary "Lallo-c, a town in this province which existed as the ancient capital until 1839 [also] Lallo-c, to twist two strands, making a string or rope."

In the classical era, Lal-lo was the home of hunter-gatherers who were specialized in hunting mollusks. These hunter-gatherers stockpiled their leftover mollusk shells in numerous sites in Lal-lo and neighboring Gattaran; eventually, the shells formed the largest stock of shell-midden sites in the entire Philippines.

The first European to set foot on what is now the town of Lal-lo was Juan de Salcedo, a Spanish conquistador and grandson of Miguel Lopez de Legazpi, in 1572. Don Juan Pablo Carrión established it as a pueblo (municipality) in 1581 and named it Nueva Segovia. The reason is currently unknown, as the hometown of Carrión was Carrión de los Condes (Palencia, Spain), as suggested by his last name. This is mentioned by Juan Miguel Aguilera and Ángel Miranda in their book Espadas del Fin del Mundo (2016). A founding population of 200 Spanish citizens from Europe accompanied by 100 Spanish soldiers set up settlements across Cagayan Valley, headed by the city of Nueva Segovia (Old Lal-lo). These people were in turn supplemented by 155 Latin American soldiers recruited from Mexico.

In 1595, Pope Clement VIII created the Diocese of Nueva Segovia. In 1596, the Dominicans accepted it as an ecclesiastical mission. Nueva Segovia had three churches: the cathedral that was under the secular clergy, and the parishes of Centro and Tocolona under the supervision of the Dominicans. Because of its distance from Manila and the constant threat of the Cagayan River's rampaging waters, however, the Diocese of Nueva Segovia was transferred to Vigan in Ilocos Sur province in 1758. The diocese's name went along with the transfer to Vigan and to avoid confusion, Bishop Miguel Garcia requested that Nueva Segovia and its suburbs renamed back to Lal-lo. The seat of the Diocese of Nueva Segovia remains in Vigan till today where is now elevated as the Archdiocese of Nueva Segovia.

The transfer affected the closure of the cathedral and the merging of the three churches into the single parish of Centro. The two other churches were abandoned and eventually destroyed because of neglect while the church of Centro, dedicated to Santo Domingo de Guzman (Saint Dominic), became what is now Lal-lo Church. The remains of three bishops are interred in the church: Bishop Miguel de Benavides who was Nueva Segovia's first bishop and later of Manila where he founded the University of Santo Tomas, Bishop Diego de Soria who was the second bishop of the diocese, and Bishop Diego Aduarte who was the sixth.

Lal-lo remained the capital of Cagayan province until 1839 when the provincial seat of power was relocated to Tuguegarao; its transformation into the most important town in Cagayan led to the decline of Lal-lo. It was accepted as an ecclesiastical mission by the Dominicans in 1604, 23 years after the foundation of Lal-lo.

The first attempt of the restoration of Lal-lo's city status was made during the first term of Mayor Florante Pascual. The historical document originally signed by King Philip was not found, even after sending a research delegation to Madrid. Pascual determined that the restoration of Lal-lo's cityhood be made through an earlier bill.

There was a move in the Philippine Congress to regain its cityhood as a component city, and also rename the municipality back to its original name, Nueva Segovia.

Renewed attempt of city status restoration was carried out in January 2012. Board member Maria Olivia Pascual said that researchers had found a Spanish document that declared the municipality as a city. According to Pascual, a bill seeking the restoration of the city status of Lal-lo (the former Ciudad Nueva Segovia) could be filed again through the efforts of First District Representative Juan Ponce Enrile, Jr.

As recently as 2018, vice mayor Oliver Pascual has said that the establishment of Northern Cagayan International Airport in the municipality would be "a great boost" in its bid for the restoration of its city status.

In 2006, the shell-midden sites of Lal-lo and Gattaran were included in the UNESCO Tentative List for World Heritage Site inclusion, a step closer to becoming a world heritage site. The shell-midden sites are currently being conserved by the local government from looting to preserve its outstanding universal value. In 2023, the government identified Lal-lo airport as a venue for American military forces as part of the Enhanced Defense Cooperation Agreement (EDCA).

Lal-lo is politically subdivided into 35 barangays. Each barangay consists of puroks while some have sitios.

Population census of Lal-lo

Year Pop. ±% p.a. 1903 7,309 —     1918 9,385 +1.68% 1939 12,921 +1.53% 1948 10,730 −2.04% 1960 16,834 +3.82% 1970 21,400 +2.43% 1975 24,866 +3.06% 1980 26,947 +1.62%	Year Pop. ±% p.a. 1990 31,373 +1.53% 1995 32,156 +0.46% 2000 36,529 +2.77% 2007 39,607 +1.12% 2010 41,388 +1.61% 2015 44,506 +1.39% 2020 48,733 +1.80%
Source: Philippine Statistics Authority

In the 2020 census, the population of Lal-lo, Cagayan, was 48,733 people, with a density of 69 inhabitants per square kilometre or 180 inhabitants per square mile.

Poverty incidence of Lal-lo

5 10 15 20 2006 15.30 2009 16.67 2012 15.54 2015 11.09 2018 13.51 2021 10.51 Source: Philippine Statistics Authority

Lal-lo, belonging to the first legislative district of the province of Cagayan, is governed by a mayor designated as its local chief executive and by a municipal council as its legislative body in accordance with the Local Government Code. The mayor, vice mayor, and the councilors are elected directly by the people through an election which is held every three years.

Members of the Municipal Council
(2022–2025)

Position	Name
Congressman	Ramon C. Nolasco Jr.
Mayor	Florante C. Pascual
Vice-Mayor	Maria Olivia B. Pascual
Councilors	Crystalyn Mae D. Invierno
	Simeon O. Israel Jr.
	Rowyn Rowel M. Samonte
	Monette V. Caliva
	Gayleen S. Durupa
	Jimmy P. Balatico
	Jimmy C. Bacuyag
	Winston L. Rosales

The Schools Division of Cagayan governs the town's public education system. The division office is a field office of the DepEd in Cagayan Valley region. The office governs the public and private elementary and high schools throughout the municipality.

• Lal-lo National High School
• Cagayan State University - Lal-lo Campus
• Lyceum of Lal-lo
• Cabayabasan National High School
• Logac National High School
• Magapit National High School

Lal-lo has one FM station, DWRL 95.1, and two cable providers.

• Philippine Standard Geographic Code
• Philippine Census Information