Cospaia is an Italian hamlet (frazione) of the comune of San Giustino in the Province of Perugia, Umbria.

The village became accidentally independent in 1440. When Pope Eugene IV ceded the territory of Sansepolcro to the Republic of Florence, by mistake a small strip of land was excluded from the treaty that delimited the borders. Having become no one's land, the inhabitants promptly declared independence. As a result, the village was the Republic of Cospaia for some 385 years, but in 1826 it was absorbed into the Papal States by agreement with the Grand Duchy of Tuscany.

Cospaia is located in the northern suburbs of San Giustino, by a lake and next to the borders of Umbria with Tuscany. It is 3 km from Sansepolcro (in the Province of Arezzo), 15 from Città di Castello, 42 from Arezzo and 67 from Perugia.

• Republic of Senarica
• List of historic states of Italy

• Ascani, Angelo (1963). Cospaia: storia inedita della singolare Repubblica. Tuscany: Città di Castello.
• Natali, Filippo (1892). La stato libero di Cospaia: nell'alta Valle del Tevere (1440-1826). Umbertide: stab. tip. Tiberino.

Media related to Cospaia at Wikimedia Commons

• Thayer's Gazetteer
• La storia ritrovata: La Repubblica di Cospaia (in Italian)
• Cospaia: storia della repubblica più piccola al mondo (in Italian)
• Flag of Cospaia Republic