Aromatic rice is an important commodity for international trade, which has encouraged the interest of rice breeders to identify the genetic control of rice aroma. The recessive Os2AP gene, which is located on chromosome 8, has been reported to be associated with rice aroma. The 8-bp deletion in exon 7 is an aromatic allele that is present in most aromatic accessions, including the most popular aromatic rice varieties, Jasmine and Basmati. However, other mutations associated with aroma have been detected, but the other mutations are less frequent. In this study, we report an aromatic allele, a 3-bp insertion in exon 13 of Os2AP, as a major allele found in aromatic rice varieties from Myanmar. The insertion is in frame and causes an additional tyrosine (Y) in the amino acid sequence. However, the mutation does not affect the expression of the Os2AP gene. A functional marker for detecting this allele was developed and tested in an aroma-segregating F(2) population. The aroma phenotypes and genotypes showed perfect co-segregation of this population. The marker was also used for screening a collection of aromatic rice varieties collected from different geographical sites of Myanmar. Twice as many aromatic Myanmar rice varieties containing the 3-bp insertion allele were found as the varieties containing the 8-bp deletion allele, which suggested that the 3-bp insertion allele originated in regions of Myanmar.