Stemnitsa (Greek: Στεμνίτσα) is a mountain village in the municipal unit of Trikolonoi, Arcadia, Peloponnese, Greece.

Stemnitsa is a traditional settlement and is considered one of the most beautiful villages in Arcadia, due to its picturesque location and its historical churches and mansions.

Due to its remote location Stemnitsa served as a relatively safe haven from the Ottomans, and it became a centre of Greek culture and religion.

The first mention, some say, of the word Stemnitsa, was found in Ottoman taxation documents dated 1512-1515 where the number of families appeared to be about 120.

[citation needed] Stemnitsa was a shelter for the Kolokotronis clan and other fighters of the Greek War of Independence.

After the revolution of March 25, 1821, from the end of May to mid of June 1821, it served as the first seat of the "Peloponissiaki Gerousia", the temporary government of the liberated Peloponnese.

Seven kilometers from Stemnitsa, down by the ravine of the river Lousios one can find the monastery of St. John the Baptist (Prodromos) built, according to some sources, around 1167, on the side of a rock face.