|Abstract:||The two main objectives of this study are as follows: first, completion of a taxonomic revision of the species of Leptosphaeria described from plant species in Ranunculaceae, Papaveraceae and Magnoliaceae; second, completion of a taxonomic revision of L. vagabunda and its infraspecific taxa. Twenty-six taxa described from species in three plant host families, Ranunculaceae, Papaveraceae and Magnoliaceae, and L. vagabunda and its six infraspecific taxa were reexamined, redescribed and illustrated from type and authentic materials. Previous disposition of six species, L. bocconiae, L. haematites, L. umbrosa, L. papaveris, L. vitalbae and L. weberi was confirmed. Two new species, L. clematicola and L. niesslii were described and illustrated. A new genus, Barrella, was established for L. thalictri. The remaining species were transferred to various genera of Loculoascomycetes and Hymenoascomycetes. There was no morphological basis to support the present classification of L. vagabunda and its six infraspecific taxa. Leptosphaeria vagabunda which has morphological characters found in the Melanommatales, was transferred to the genus Melanomma and its five infraspecific taxa were assigned at species level to separate genera in Pleosporales and Melanommatales. The new genus Biclypeosphaeria, typified by L. vagabunda f. salicis-capreae, was established to include the foregoing species and L. vagabunda f. lonicerae. Leptosphaeria vagabunda f. salicis-purpureae was a synonym of L. vagabunda f. salicis-capreae.