The Aśvakas (Sanskrit: अश्वक), also known as the Ashvakas, Aśvakayanas or Asvayanas and sometimes Latinised as Assacenii/Assacani, were a people who lived in what is now north-eastern Afghanistan and the Peshawar Valley. The region in which they lived is also called Aśvaka and should not be confused with the similarly named mahajanapada (great country) of south India that is recorded in ancient Buddhist texts. The word is also used as a generic descriptor for nomadic pastoral peoples of ancient north-western ancient India, who were known for their skills as horse breeders and equestrians.
The Sanskrit term aśva, Iranian aspa and Prakrit assa means horse. The name Aśvaka/Aśvakan or Assaka is derived from the Sanskrit Aśva or Prakrit Assa and it denotes someone connected with the horses, hence a horseman, or a cavalryman or horse breeder. The Aśvakas were especially engaged in the occupation of breeding, raising and training war horses, as also in providing expert cavalry services.
Ancient Greek historians who documented the exploits of Alexander the Great refer to the Aspasioi and Assakenoi tribes among his opponents. The historian Ramesh Chandra Majumdar has said that these words are probably corruptions of Aśvaka. It is possible that the corruption of the names occurred due to regional differences in pronunciation. Rama Shankar Tripathi thinks it possible that the Assakenoi were either allied to or a branch of the Aspasioi. The Greeks recorded the two groups as inhabiting different areas, with the Aspasioi in either the Alishang or Kunar Valley and the Assakenoi in the Swat Valley.