Karasu is a neighborhood in Tonya District, in Trabzon Province, Türkiye. Karasu lies at 702 m above sea level, in the Rize Dağları mountains. It has 204 inhabitants. The nearest city is Akçaabat, 24 km to the east. Among the landmarks around are Sumela Monastery (42 km), Hagia Sophia (34 km) and Vazelon Monastery (29 km).