Harmanli is a town in Haskovo Province, South-central Bulgaria. It is the administrative centre of the homonymous Harmanli Municipality. Harmanli came into being in about 1510 along the road that connects Central Europe and Anatolia.
Its territory spreads over some parts of the Upper Thracian Lowlands between the oblique south slopes of the Sredna Gora and precipitous north slopes of the Rhodope Mountains. The south boundary of the Thracian lowlands is outlined by the north Rhodope foot, along which it leans close on the north Rhodopes, between the lower end of the Momina Klisura defile (at 300 m elevation) and the beginning of the Harmanli defile (at 80 m elevation).