This study was conducted to obtain baseline data describing Allium monanthum Max. for breeding an elite cultivar. A. monanthum has recently become popular vegetable in Korea owing to its unique flavors and nutraceutical effects. The agronomic traits of 271 accessions of A. monanthum collected throughout Korea were evaluated in this study. Leaf width showed the greatest variation (0.1 to 25 mm) among traits evaluated, followed by leaf sheath length and number of cormlets. The average leaf sheath length and diameter, which are commonly used to evaluate quality in the market, were 1.29 cm and 0.3 cm. Some superior accessions had a leaf sheath length of >10 cm and diameter of >1.1 cm. The average weight of the cormlets ranged from 1 to 2 g; however, one accession weighed more than 4 g. The genetic diversity of A. monanthum calculated based on morphology and molecular distance was greater in Jeolla and Gyeoungsang provinces than Gyeonggi and Chungcheong provinces. Finally, seven elite accessions of A. monanthum were selected owing to their potential usefulness in future breeding projects.