Cohors secunda Aquitanorum equitata civium Romanorum ("2nd part-mounted Cohort of Aquitani Roman citizens") was a Roman auxiliary mixed infantry and cavalry regiment. It was probably originally raised in Gallia Aquitania in the reign of founder-emperor Augustus after the revolt of the Aquitani was suppressed in 26 BC. Unlike most Gauls, the Aquitani were not Celtic-speaking but spoke Aquitanian, a now extinct non Indo-European language closely related to Basque. The regiment was also known as cohors II Biturigum. The Bituriges were a Celtic-speaking tribe whose territory was included in Gallia Aquitania. It is believed that when the Aquitani regiments were originally raised (probably in two series), some were made up of mixed Aquitani and Bituriges recruits.