Ilagan River

{{Short description|River in north Luzon, Philippines}}

{{Use mdy dates|date=September 2024}}

{{Infobox river

| name = Ilagan River

| name_native = {{native name|ilo|Pinacauan De Ilagan}}

| name_native_lang =

| name_other =

| name_etymology =

| image = San_Mariano_Isabela.JPG

| image_size = 200

| image_caption = The Ilagan River as it passes through the municipalities of San Mariano (background) and Benito Soliven (foreground).

| map =

| map_size = 250 px

| map_caption = Drainage area of the Ilagan River and its tributaries on the island of Luzon, Philippines

| pushpin_map = Luzon mainland#Philippines

| pushpin_map_size =

| pushpin_map_caption= Ilagan River mouth

| subdivision_type1 = Country

| subdivision_name1 = Philippines

| subdivision_type2 = Region

| subdivision_name2 = Cagayan Valley

| subdivision_type3 = Province

| subdivision_name3 = Isabela

| subdivision_type4 =

| subdivision_name4 =

| subdivision_type5 =

| subdivision_name5 =

| length = {{convert|189|km|mi|abbr=on}}

| width_min =

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| discharge1_location=

| discharge1_min =

| discharge1_avg = {{convert|270|m3/s|cuft/s|abbr=on}}{{cite web|title=The Cagayan River Basin|url=http://www.abs-cbnnews.com/research/10/23/09/cagayan-river-basin|work=ABS-CBN News|accessdate=March 20, 2014}}

| discharge1_max =

| source1 = Sierra Madre mountains

| source1_location = Casiguran, Aurora, Central Luzon

| source1_coordinates= {{coord|16|18|42|N|121|59|6|E|dim:15000_region:PH_type:river|display=inline}}

| source1_elevation =

| mouth = Cagayan River

| mouth_location = Ilagan, Isabela

| mouth_coordinates = {{coord|17.16763|N|121.89039|E|format=dms|dim:15000_region:PH_type:river|display=inline,title}}

| mouth_elevation =

| progression = Ilagan River – Cagayan River

| river_system =

| basin_size = {{convert|3132|km2|abbr=on}}

| tributaries_left =

| tributaries_right = {{hlist|Abuan River|Bintacan River}}

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The Ilagan River, also known as the Pinacanauan de Ilagan River,{{cite book |last=Salgado|first=Pedro|title=Cagayan Valley and Easter Cordillera: 1581-1898, Volume I |publisher=Rex Publishing |orig-date=2002|page=7|chapter=Cagayan Valley at the Arrival of the Spaniards|isbn=}} is a river in the province of Isabela, Cagayan Valley, Philippines. It is one of the major tributaries of the Cagayan River, the largest river in the Philippines. The Ilagan River originates from the western slopes of the Sierra Madre and drains the eastern central portion of the Cagayan River basin. It has an estimated catchment basin size of {{convert|3132|km2}}{{cite web|title=Cagayan Riverine Zone Development Framework Plan|url=http://rdc.rdc2.gov.ph/docs/Cagayan|publisher=National Economic and Development Authority-Regional Development Council Region 2|accessdate=March 20, 2014}}{{Dead link|date=January 2020 |bot=InternetArchiveBot |fix-attempted=yes }} and an estimated annual discharge of 9,455 million cubic meters/s. It flows westward and joins the Cagayan River in Ilagan, Isabela.