The ao dai (Vietnamese: 醥 d鄆) is a Vietnamese national costume; now most commonly for women. In its current form; it is a tight-fitting silk tunic worn over pantaloons. The word is pronounced [a?wz?j]. 羙 is derived from a Middle Chinese word meaning 'padded coat' (?). D鄆 means 'long'.

The word 'ao dai' was originally applied to the outfit worn at the court of the Nguy?n Lords at Hu? in the 18th century. This outfit evolved into the 醥 ngu th鈔; a five-paneled aristocratic gown worn in the 19th and early 20th centuries. On T?t and other occasions; Vietnamese men may wear an 醥 g?m (brocade robe); a version of the ao dai made of thicker fabric.