Blatná Polianka (Hungarian: Sárosmező, Rusyn: Блатна Полянка) is a village and municipality in the Sobrance District in the Košice Region of east Slovakia.

In historical records the village was first mentioned in 1417. Before the establishment of independent Czechoslovakia in 1918, Blatná Polianka was part of Ung County within the Kingdom of Hungary. In 1939, it was for a short time part of the Slovak Republic. As a result of the Slovak–Hungarian War of 1939, it was again part of Hungary from 1939 to 1944. In the autumn of 1944, the Red Army entered Blatná Polianka and it was once again part of Czechoslovakia.

The village lies at an altitude of 104 metres and covers an area of 9.986 km². It has a population of about 170 people.

The village has a public library and a football pitch

The records for genealogical research are available at the state archive "Statny Archiv in Presov, Slovakia"

• Greek Catholic church records (births/marriages/deaths): 1834–1895 (parish B)
• Reformated church records (births/marriages/deaths): 1797–1916 (parish B)

• List of municipalities and towns in Slovakia

• http://en.e-obce.sk/obec/blatnapolianka/blatna-polianka.html
• https://web.archive.org/web/20071116010355/http://www.statistics.sk/mosmis/eng/run.html
• http://www.blatnapolianka.sk
• Surnames of living people in Blatna Polianka

48°41′N 22°06′E / 48.683°N 22.100°E / 48.683; 22.100