Gedrosia (; Greek: Γεδρωσία) is the Hellenized name of the part of coastal Baluchistan that roughly corresponds to today's Makran. The area which is named Gedrosia, in books about Alexander the Great and his successors, runs from the Indus River to the southern edge of the Strait of Hormuz. It is directly to the south of the countries of Bactria, Arachosia and Drangiana, to the east of the country of Carmania and due west of the Indus River which formed a natural boundary between it and Western India. The native name of Gedrosia might have been Gwadar as there are two towns by that name and a bay (Gwadar Bay) in central Makran.
Following his army's refusal to continue marching east at the Hyphasis River in 326 BCE, Alexander the Great crossed the area after sailing south to the coast of the Indian Ocean on his way back to Babylon. Upon reaching the Ocean, Alexander the Great divided his forces in half, sending half back by sea to Susa under the command of Nearchus. The other half of his army was to accompany him on a march through the Gedrosian desert, inland from the ocean. Throughout the 60-day march through the desert, Alexander lost at least 12,000 soldiers, in addition to countless livestock, camp followers, and most of his baggage train. Some historians say he lost three-quarters of his army to the harsh desert conditions along the way. However, this figure was likely based on exaggerated numbers in his forces prior to the march, which were likely in the range of no fewer than 30,000 soldiers.
There are two competing theories for the purpose of Alexander's decision to march through the desert rather than along the more hospitable coast. The first argues that this was an attempt to punish his men for their refusal to continue eastward at the Hyphasis River. The other argues that Alexander was attempting to imitate and succeed in the actions of Cyrus the Great, who had failed to cross the desert.
After the death of Alexander, this region became part of the holdings of Seleucus, who also held Ariya (modern-day Kabul), Gedrosia (Baluchistan), Arakeshiya (Kandhar), and Peripemisdai (Herat). The territories, known collectively as Ariyana were later lost to the Mauryan Empire.