Aydemir (, also Aidemir, Ajdemir) is a village in northeastern Bulgaria, part of Silistra Municipality, Silistra Province. As of 2007, it is the most populous village in Bulgaria, with a population of 7,815 according to 2005 data. Aydemir lies at , 31 m above sea level. The village is located in the valley of the Danube, 3 km south of the river and 8 km west of Silistra, on the road from Silistra to Rousse. The mayor is Rumen Angelov.
Aydemir is divided into three parts: the centre, the quarter of Delenkite and the quarter of Tataritsa, which was founded in 1674 by Old Believer Nekrasov Cossacks (see Russians in Bulgaria) at a location prior to that inhabited by Tatars.
The village has a church, the Church of the Holy Trinity, which was constructed in 1829. For a certain period, it was named Knyaz Hesenski (Княз Хесенски, " Grand Duke of Hesse") in honour of Alexander I Battenberg, the first monarch of modern Bulgaria.
According to Ancho Kaloyanov, the name of the village is derived from Greek άγιος (agios, " Saint") and the shortening of the personal name Demetrius, i.e. " Saint Demetrius", both through Turkic.
In 1924, a 14th-century treasure comprising 101 silver coins, including some of Tsar Ivan Alexander of Bulgaria, was discovered near the village.