阿拉霍西亚（Arachosia）是古代阿契美尼德帝国、塞琉西帝国、孔雀王朝及帕提亚帝国的一个行省的希腊名称，它包括现今阿富汗东南部及巴基斯坦和印度的部份地区。赫尔曼德河（Helmand River）流经阿拉霍西亚并提供南阿富汗最肥沃的土地。当中最大的城市坎大哈，据说是由亚历山大大帝创建及命名。

阿拉霍西亚在巴克特里亚正南方，以兴都库什山脉为界。南面是格德罗西亚（即现今俾路支省）、西面是德兰吉安纳（现今锡斯坦），而东面则是印度河。西北地区有Pactyans，一个古印度–依朗部族（梨俱吠陀的Pakthas），他们可能是现今普什图族的祖先。南及东南区有Rhoplutae人（据信是印度的罗布拉人Rohilla、拉杰普特人Rajputs及阿富汗人Afghans的祖先）和Eoritae（阿腊塔人Arattas或Aroras）。

Arachosia /ærəˈkoʊsiə/ is the Hellenized name of an ancient satrapy in the eastern part of the Achaemenid, Seleucid, Parthian, Greco-Bactrian, and Indo-Scythian empires. Arachosia was centred on Arghandab valley in modern-day southern Afghanistan, and extended east to as far as the Indus River in modern-day Pakistan. The main river of Arachosia was called Arachōtós, now known as the Arghandab River, a tributary of the Helmand River. The Greek term "Arachosia" corresponds to the Aryan land of Harauti which was around modern-day Helmand. The Arachosian capital or metropolis was called Alexandria or Alexandropolis and lay in what is today Kandahar in Afghanistan. Arachosia was a part of the region of ancient Ariana.