The existence of two baths, if not more, in Roman Ankara reveals that a considerable amount of water was needed at least for the working of these baths. However, how and from where this water was supplied is not so clear because of the lack of both archaeological and historical evidence. In this regard, by bringing together all the archaeological data so far discovered and the available published information regarding the water supply scheme in order to see all this data collectively in a single picture, this thesis tries to investigate how and from where the water was supplied to Roman Ankara. In addition, this thesis reviews the available water potential of Ankara considering geography and hydrology of the site and also contains an analysis of how water was supplied in the more recent history of the city which is believed to contain invaluable information regarding the ancient water supply scheme of the city especially when the archaeological data is very scarce.