National Route 1 (N1) is a primary national route that forms part of the Philippine highway network, running from Luzon to Mindanao. Except for a gap in Metro Manila and ferry connections, the highway is generally continuous. Most sections of N1 forms the Pan-Philippine Highway except for sections bypassed by expressways.

Route description N1 follows a route that runs from Laoag in Ilocos Norte to Zamboanga City via Bicol Region, Eastern Visayas and eastern and southern parts of Mindanao. The highway connects most major regional centers on its route and runs through different landscapes. The highway is mostly named Maharlika Highway or National Highway, but other sections use different names, including alternative names assumed within some poblacions (city or town proper).

Ilocos Region

N1 begins at the intersection with N2 (Manila North Road) and N100 (Laoag Airport Road) in Laoag as Manila North Road (MaNor). It then crosses Padsan River via Gilbert Bridge and enters the city proper of Laoag, where it splits before turning to the east in front of Ilocos Norte Provincial Capitol, where the Pan-Philippine Highway commences. It then briefly follows J.P. Rizal Avenue before turning to General Segundo Avenue; both are principal city streets passing through the city proper and through its outskirts. Approaching Bacarra, it becomes a rural highway. At Bacarra, it bypasses the town center to the north and runs through a rural area, and then enters Pasuquin, where it serves as a major municipal street. Between Bacarra and Burgos, it becomes a rural two-lane highway and passes through interspersed barangays along the South China Sea coastline. It soon climbs the mountains upon approach to Burgos, where the highway directly serves the town. The highway zigzags through the rough terrain and overlooks the beach where Bangui Wind Farm lies. It then passes through Bangui, where it runs as a major street on the town center, crosses Bulu River, and enters Pagudpud, where it bypasses the town proper. N1 runs through the foothills that mark the edge of the Cordillera Central mountain range and runs close to the coastline of Babuyan Channel, where the highway zigzags through the cliffs through the Patapat Viaduct, a viaduct that is required for the highway to pass the steep cliffs marking the northern edge of the Cordillera Range.

Cagayan Valley

Entering the Cagayan Valley region, N1 follows Manila North Road up to barangay Bangag, Aparri. From there, it turns south and becomes Bangag-Magapit Road up to the Magapit Interchange in Lal-lo. Within Lal-lo, N1 is also known as Logac–Magapit Road between namesake barangays Logac and Magapit. The segment includes the Magapit Suspension Bridge, which spans over the Cagayan River before meeting the Magapit Interchange.

At the interchange, it turns southeast and becomes Cagayan Valley Road from Magapit, Lal-lo to Tuguegarao, running parallel to the Cagayan River. In Tuguegarao, N1 turns east at the roundabout intersection with N106 (Tuguegarao Diversion Road) and N51 (Santiago–Tuguegarao Road) to bypass the city proper towards Peñablanca and run parallel to the Cagayan River up to Reina Mercedes, Isabela. It then enters the province of Isabela and Nueva Vizcaya as Maharlika Highway, although it is alternatively called Cagayan Valley Road up to Guiguinto, Bulacan. It serves as the main artery of Isabela alongside N51. In Santiago, Isabela, it turns southwest at the Mabini Rotonda, its intersection with N51, and becomes a one-way northbound route. Southbound traffic is redirected via R.C. Miranda Road and Boulevard to bypass this one-way section.

At Nueva Vizcaya, N1 runs parallel to and crosses the Magat River. In Solano, it navigates through the poblacion locally as J. Manzano Street, cutting through as J.P. Rizal Avenue, and finally exiting as Aquino Avenue towards its segment bypassing Bayombong poblacion. Further in Santa Fe, it then reaches the Dalton Pass, where Sierra Madre and Caraballo Sur meet.

Although Cagayan Valley Road is limited to Cagayan, its name also alternatively extends up to N1's section in Bulacan.

Central Luzon Nueva Ecija

The highway soon enters Nueva Ecija at Carranglan. It then descends to the plain terrain in San Jose as it approaches the poblacion. It then cuts through Muñoz and Talavera before turning east by its junction with N114 (Nueva Ecija–Pangasinan Road) in Santo Domingo. It then cuts through Talavera (once again, this time with the poblacion), Cabanatuan, Santa Rosa, San Leonardo and Gapan.

Bulacan San Rafael to Guiguinto

N1 soon enters Bulacan at San Miguel, where it begins on a straight route. It then enters the poblacion of San Miguel, which it bypasses, and the highway begins to curve through most of its length between San Ildefonso and San Rafael, where the route runs through rice paddies. At its intersection with San Rafael Municipal Road, the highway curves to the southwest to follow Doña Remedios Trinidad Highway (DRT Highway) until the intersection of the old Cagayan Valley Road and Esguerra Street in Pulilan. DRT Highway serves as a bypass of the old Cagayan Valley Road through Baliwag poblacion. At Guiguinto, it crosses the North Luzon Expressway (NLEX) along with the Santa Rita Interchange, where Asian Highway 26 leaves for the expressway. Despite this split, the road continues to be known as the Maharlika Highway as it continues its course southwards up to Tabang Interchange, where it meets the original route of NLEX and MacArthur Highway (Manila North Road).

Guiguinto to Meycauayan

Past Tabang Interchange, N1 begins to follow Manila North Road once again, this time as MacArthur Highway, which serves as a major toll-free highway over southern Bulacan. It soon crosses the Philippine National Railways/North–South Commuter Railway right of way and enters Balagtas, where it directly passes through its poblacion. It soon crosses the Bigaa River, where it passes through residential and industrial areas, and curves upon entering Bocaue, where it bypasses the town center. A flyover restricted for use by light vehicles crosses Fortunato Halili Avenue to Santa Maria with service roads serving as frontage and heavy vehicle routes. The highway then curves and traverses through the residential barangays of Bocaue and soon enters Marilao and Meycauayan.

Metro Manila Valenzuela to Pasay

Entering Metro Manila, the highway follows MacArthur Highway over Valenzuela, which runs on a four to six-lane highway up to the Bonifacio Monument (Monumento) Circle in Caloocan. There, the Asian Highway 26 concurrency returns on N1 as it turns east to follow Epifanio de los Santos Avenue (EDSA) up to Pasay. The whole road, bypassing the capital city of Manila, runs through the central business districts of Metro Manila, most notably Araneta Center, Ortigas Center, and Makati Central Business District. The LRT Line 1 and MRT Line 3 utilizes the center island of EDSA on most segments between Caloocan and Pasay. N1 ends below the EDSA Flyover at N120/AH26/N61 (Roxas Boulevard) in Pasay.

A gap in the highway is filled by the South Luzon Expressway (SLEX) and Skyway between Makati and Muntinlupa. It would have been filled by Taft Avenue Extension, starting from EDSA, going southwards via Quirino and Diego Cera Avenues (N62) and ends at Manila South Road below Alabang Viaduct through Alabang–Zapote Road (N411).

Muntinlupa

N1 resumes below the Alabang Viaduct of South Luzon Expressway (SLEX/E2/AH26) in Alabang, Muntinlupa, where it intersects with SLEX's Alabang Exit, East Service Road, N411 (Alabang–Zapote Road), and N142 (Montillano Street). The highway assumes the name Manila South Road, locally National Road or Old National Road, or Maharlika Highway, although this section does not assume the Asian Highway 26 concurrency, which is designated instead to SLEX. It runs as a commercial artery through the city up to the boundary with Laguna in San Pedro over the Tunasan River.

Calabarzon San Pedro to Calamba

N1 generally serves as a four-lane toll-free highway serving the suburban cities of northwestern Laguna alongside the tolled South Luzon Expressway. Most sections of N1 between San Pedro and Calamba serve as commercial streets bypassing the old poblacions. Most of N1 is four-lane with a painted median divider.

It enters Laguna in San Pedro, where it serves as a major commercial street, with a maximum of four lanes. It then enters the cities of Biñan, Santa Rosa, Cabuyao, and Calamba, where it becomes one-way southbound between N66 (Calamba–Pagsanjan Road) and N420-2 (Rizal Shrine Road) at the Calamba Crossing. In barangay Real, the highway is alternatively known as Real Road.

Calamba to Tayabas

N1 soon crosses the South Luzon Expressway at the Calamba Exit, where the concurrency with the Asian Highway 26 returns on the highway, and veers south. It then enters the province of Batangas at Santo Tomas, where it intersects with STAR Tollway and bypasses the poblacion. At the Santo Tomas Roundabout, where it meets N4 (Jose P. Laurel Highway) and N421-2 (Governor Carpio Avenue), it turns southeast as it leaves the province. It then re-enters the province of Laguna through Alaminos and then San Pablo, bypassing its poblacion.

N1 then enters the province of Quezon at Tiaong. There, it passes the Villa Escudero plantations and meets the future Tiaong Interchange of SLEX Toll Road 4, then cuts through the poblacion as Doña Tating Street and then veers east as Don V. Robles Street. It then traverses the municipalities of Candelaria (as Rizal Avenue through the poblacion) and Sariaya (as General Luna Street through the poblacion) and the city of Tayabas, where it turns southeast towards Lucena at the Calumpang Junction.

Tayabas to Pagbilao

From Tayabas through Lucena, N1 then follows the entire Lucena Diversion Road (also known as MSR Diversion Road), a wide road that bypasses the Old Manila South Road alignment, which cuts through Lucena poblacion, up to the road's eastern end in Pagbilao.

Pagbilao to Calauag

In Pagbilao poblacion, N1 briefly splits into MSR Diversion Road (collective name for the segment locally known as C.M. Recto Street and Pornobi Street, respectively) for westbound traffic and J.P. Rizal Street for eastbound traffic. Onto the area of the protected Quezon National Forest Park in the Sierra Madre, it then becomes alternatively known as New Diversion Road, the longer road bypassing the Old Zigzag Road alignment cutting through the park.

The route enters Atimonan, bypassing the poblacion before reaching Quezon’s eastern coastline. It then continues through Plaridel and then Gumaca, where it becomes J.P. Rizal Street in the poblacion south of the Gumaca River, then shifts eastward as A. Bonifacio Street toward Lopez. Within Lopez poblacion, it is known as General Vera Avenue before traversing Calauag.

Bicol Region

Santa Elena to Sipocot

N1 enters Camarines Norte at the municipality of Santa Elena, meeting the N68 (Andaya Highway) that serves as a southern bypass of N1 which traverses the sparsely populated province of Camarines Norte. After traveling through kilometers of jungle, N1 navigates through the poblacion of Labo. It then becomes a rural highway again, passing by the municipalities of Vinzons and Talisay before bypassing Daet. It passes through Bicol Natural Park where the road winds through mountainous and hilly terrain. N1 enters Camarines Sur at the municipality of Sipocot, where it meets again N68 at its eastern end.

Sipocot to Matnog

From Sipocot, N1 traverses the municipalities of Libmanan, Pamplona, San Fernando, and Milaor (where it is alternatively known as Mabolo Road) in Camarines Sur. N1 then enters Naga City, bypassing its poblacion as Roxas Avenue or Diversion Road before turning east at the Naga Rotonda to follow Maharlika Highway to enter Pili, the provincial capital. It then traverses the municipalities of Bula, Baao, Nabua, and Bato.