The previous taxonomic treatments of Paeonia arietina (=P. mascula subsp. arietina) and studies on relationships with its allies are reviewed. As a result of examination of a large number of herbarium specimens, extensive field observations, population sampling in the Mediterranean region, Turkey and the Balkan, and subsequent analysis, the P. arietina-P. parnassica group is found to be distinct from P. mascula in having tuberous roots, hersute stems, petioles and sepals, and leaves that are mostly densely villose beneath. Our morphological and molecular data indicate that the P. arietina-P. parnassica group is most closely related to the P. officinalis group. These two groups are clearly separated from each other by differences in the indumentum of the sepals and stems, and in the shape, number and indumentum of the leaflets/segments. Paeonia parnassica is distinguished from P. arietina mainly by the dark purple petals (vs. pink or red) and purple anthers (vs. yellow). paeonia officinalis supsp. banatica can not be clearly distinguished from P. officinalis subsp. officinalis. As a result, P. arietinal and P. parnassica are recognized at specific rank, whilst P. officinalis subsp. banatica is retained as a subspecies.