Psou

{{Infobox river

| name = Psou

| image = Река Псоу - panoramio.jpg

| image_caption =

| pushpin_map = Georgia Abkhazia#Georgia

| source1_location = Greater Caucasus

| mouth_location = Black Sea

| mouth_coordinates = {{coord|43.3861|N|40.0101|E|source:wikidata-and-enwiki-cat-tree_region:RU|display=it}}

| subdivision_type1 = Country

| subdivision_name1 = Georgia (Abkhazia{{Abkhazia-note}}), Russia

| length = {{convert|53|km|mi|abbr=on}}

| source1_elevation =

| mouth_elevation =

| discharge1_avg =

| basin_size = {{convert|421|km2|mi2|abbr=on}}

}}

The Psou ({{IPAc-en|p|s|oʊ}}; {{langx|ady|Псыу}}; {{lang-ka|ფსოუ}}; {{langx|ab|Ԥсоу}}; {{langx|ru|Псоу}}) is a river in the West Caucasus, bordering the Gagra Range to the east. It flows along the southern slopes of the Greater Caucasus Mountain Range and forms a part of the border between Georgia (Abkhazia) and Russia. Its source is in the Aigra Mountain, and it flows into the Black Sea. The Psou is {{convert|53|km|mi}} long, and the drainage basin is approximately {{convert|421|km2|mi2}}.{{cite book|title=Our Waters: Joining Hands Across Borders : First Assessment of Transboundary Rivers, Lakes and Groundwaters|url=https://books.google.com/books?id=L73CJCH-ZuIC&pg=RA1-PA1|year=2007|publisher=United Nations. Economic Commission for Europe, United Nations Publications|isbn=978-92-1-116972-0|page=149}} Between the mouth of the river and the mouth of the Mzymta is a "sandy depositional foreland", which is approximately {{convert|8|km}} in length and {{convert|2|km}} wide.{{cite book|last=Bird|first=Eric|title=Encyclopedia of the World's Coastal Landforms|url=https://books.google.com/books?id=Mfo5TPb7SDsC&pg=PA813|date=25 February 2010|publisher=Springer Science & Business Media|isbn=978-1-4020-8638-0|page=813}}

The principal tributaries of the Psou are the Besh and the Pkhista. Between 1913 and 1955, a hydrological station was in operation at Leselidze, roughly {{convert|1.5|km}} upstream of the river's mouth.

The Psou gained notoriety as a smuggling route out of the country, by-passing Russian controls on the border.{{cite book|last1=Gori|first1=Umberto|last2=Paparela|first2=Ivo|title=Invisible Threats: Financial and Information Technology Crimes and National Security|url=https://books.google.com/books?id=_GNqA6X_G_8C&pg=PA119|year=2006|publisher=IOS Press|isbn=978-1-58603-664-5|page=119}}{{cite book|last1=Cornell|first1=Svante|last2=Jonsson|first2=Michael|title=Conflict, Crime, and the State in Postcommunist Eurasia|url=https://books.google.com/books?id=vO_DBwAAQBAJ&pg=PA115|date=11 January 2014|publisher=University of Pennsylvania Press|isbn=978-0-8122-0898-6|page=115}} As of 2008 it was still designated as a transboundary river which lacked an international cooperation agreement as part of the UNECE Water Convention.{{cite book|last=Lagutov|first=Viktor|title=Rescue of Sturgeon Species in the Ural River Basin|url=https://books.google.com/books?id=7xmZ2jIOGQsC&pg=PA33|date=22 October 2008|publisher=Springer Science & Business Media|isbn=978-1-4020-8924-4|page=33}}