The Ahja is a river in Estonia. The river is long. The river begins at Lake Erastvere and empties into the River Emajõgi.
jõgi, Läänistel, 2008.jpg|The Ahja in Lääniste in 2008 Ahja near Valgemetsa | Kiidjärve watermill, built in 1914 Taevaskoda 2011.jpg| Taevaskoja
Ahja is a small borough () in Ahja Parish, Põlva County in southeastern Estonia. Named after the Ahja River, it is located 191 km southeast of Tallinn and about 16 km north of Põlva.