Bactria or Bactriana was the name of a historical region in Central Asia. The English name Bactria is derived from the Ancient Greek: Βακτριανή, a Hellenized version of the Bactrian endonym Bakhlo (βαχλο). Analogous names include the Pashto and Persian: باختر, translit. Bākhtar, Uzbek: Балх, Tajik: Бохтар, Chinese: 大夏; pinyin: Dàxià, and Sanskrit: बाह्लीक, translit. Bāhlika. Bactria was located between the Hindu Kush mountain range and the Amu Darya river, covering the flat region that straddles modern-day Afghanistan, Uzbekistan and Tajikistan.
According to Pierre Leriche:
Bactria, the territory of which Bactra [Balkh] was the capital, originally consisted of the area south of the Āmū Daryā with its string of agricultural oases dependent on water taken from the rivers of Balḵ (Bactra) [Balkh], Tashkurgan, Kondūz [Kunduz], Sar-e Pol, and Šīrīn Tagāō [Shirin Tagab]. This region played a major role in Central Asian history. At certain times the political limits of Bactria stretched far beyond the geographic frame of the Bactrian plain.