Before the ao dai was considered our traditional costume, we had the ao tu than, which translates as the four-flapped dress.

The dress is long-sleeved and usually dark brown, with two front and two back "flaps," or strips of fabric. The two back flaps are sewn together with a seam running down the spine, called the dress's spine. The two flaps in front are not sewn together but are attached to the back flaps as the well as the sleeves. These two front flaps are knotted in front of the waist. Two blue or light green sashes are wrapped around behind the waist over the back flaps like a belt and tied together with the two front flaps. Together, the front flaps and the sashes dangle like ribbons and move with the rhythm of the woman's steps. Beneath the dress is a worn a white or bright pink yem, a diamond shaped piece of fabric that covers the chest and has straps from the right and left corners to tie be tied around the back and straps at the collar to secure it around the neck. The bottom corner of the yem is tucked under a long black skirt worn beneath the dress. From the 17th through the 19th century, Vietnamese women wore ao tu than with skirts to differentiate themselves from men, who wore a similar costume with pants. In 1928, during the Nguyen dynasty, Emperor Minh Mang ordered women to wear pants instead of skirts. However, until the 10th century, the familiar costume of young women of the Northern countryside remained an ao tu than and a skirt of rough cloth.