Reseda microcarpa subsp. zanjanica is described as a new subspecies from Zanjan province (NW Iran). Morphological and micromorphological characteristics (flowers, leaves, inflorescences, fruits, seeds, and pollen grains), habitat features (ecological conditions that influenced the growth of this taxon such as altitudes and growing beds), distribution, taxonomic notes, and conservation status (IUCN Red List categories and criteria) are provided and compared for new subspecies and R. microcarpa subsp. microcarpa. Moreover, statistical analysis by multi-variate statistical analyses software (MVSP) segregated both the taxa based on morphological and micromorphological characteristics (quantitative and qualitative) with Principal Components Analysis (PCA). All characteristics formed three groups (group B: plant height and inflorescence length, group C: polar pollen axis and minimum and the average of colpus measurements, and group A: includes the rest studied morphological and micromorphological characteristics) except one characteristic (i.e. maximum size of colpus measurements) and two groups had high value for segregation of both taxa based on the statistical analysis (group C for R. microcarpa subsp. microcarpa, and group B for the new subspecies). Although, characteristic group A was valuable in the position of both taxa, the maximum size of colpus had the lowest value.
