In this study, sixteen isolates of Magnaporthiopsis maydis were isolated from infected maize (Zea mays L.) plants collected from different governorates in Egypt. These isolates were identified at the molecular level using a specific primer. All isolates have the same growth pattern form (rhizoid), growth elevation (raise) and growth margin (filiform) on PDA medium but differed in color. The faster isolate in growing on PDA medium was isolate S3 while the slower one was A2. The analysis of variance showed significant differences among isolates. The pathogenicity test was carried out under greenhouse conditions using a Single cross pioneer 3062 hybrid. Isolates F13 and F14 were highly aggressive (33.33%), while isolate Mi5 was the lowest (10%). No correlation was detected between disease incidence and radial growth of M. maydis isolates. Genetic diversity among isolates was studied using six RAPD markers and showed a high similarity percentage (95%) between isolate F13 and F14 and between isolate F14 and F15.Whereas, the lowest similarity percentage (26%) was between isolate A2 and KS11. The Cluster analysis using the Dice coefficient divided the studied isolates into five clusters. Cluster 1 contains isolates nos. F14, F15, F13, B12, KS7, and KS16, cluster 2 contains isolates nos. F9, M10, Mi5, and M8, cluster3 contains isolates nos. S3, KS6, and F1-B4, cluster 4 contains isolate number KS11 and cluster 5 contains isolate number A2.