River Derg

{{Short description|River in Counties Donegal and Tyrone on the island of Ireland}}

{{Use dmy dates|date=September 2020}}

{{EngvarB|date=September 2020}}

{{Infobox river

| name = River Derg

| image = The Ardstraw bridge viewed from downstream - geograph.org.uk - 1322092.jpg

| image_caption = River Derg and the Ardstraw Bridge

| name_etymology = From Lough Derg, 'red lake'

| name_native = {{native name|ga|Abhainn na Deirge}}

| source1_location = Lough Derg, County Donegal, Republic of Ireland

| mouth = River Mourne

| mouth_coordinates = {{coord|54.7378|-7.4304|format=dms|display=inline,title|region:GB-NIR_type:river}}

| subdivision_type1 = Country

| subdivision_name1 = Republic of Ireland, Northern Ireland

| length = {{Convert|45|km|mi}}

| source1_elevation = {{Convert|138|m|ft}}

| discharge1_avg = {{convert|16.2|m3/s|abbr=on}}

| basin_size = {{Convert|440|km2|sqmi}}

}}

File:River Derg - geograph.org.uk - 698964.jpg]]

The River Derg is a small river in Ireland. The river has its source in Lough Derg, in County Donegal, Republic of Ireland, and it flows into County Tyrone, Northern Ireland, east through Castlederg to join with the River Strule to form the River Mourne. The upper reaches of the catchment are characterised by peatland, while the lower reaches flow predominantly through farmland.[http://www.loughs-agency.org/discover/fishing/rivers/derg Derg] {{Webarchive|url=https://web.archive.org/web/20160303232416/http://www.loughs-agency.org/discover/fishing/rivers/derg |date=3 March 2016 }} Lough Foyle

The River Derg's length is {{convert|28|mi|km}}.Ordnance Survey of Ireland: Rivers and their Catchment Basins 1958 (Table of Reference)

The River Derg is known for its salmon, grilse and sea trout.{{fact|date=September 2020}}